enigmatic puzzle - Twisted Connections

_{This is an entry into the Fortnightly Topic Challenge #36}

The following is an Only-Connect wall seen in the BBC TV series. You have to divide the 16 words into groups of 4 each satisfying a specific condition.

Now, before you complain, the 16 words aren't given. Instead, you have been given Cryptic Clues that clue the words.

Next, after getting the words, you find out the groups of 4 and the relations between the words in the respective groups. So, you should get 4 words/phrases as your answer(this is where the game normally stops).

However, I can't stop there. So, next, using those 4 words/phrases, you have to find out another 4 words/phrases(How, you ask? That's the real puzzle)

Your final job is to create another only-connect wall with those groups of 4 words/phrases as the connections.

Answer

Here's my working so far, for the clues I've been able to figure out. I'll keep plugging away and update as I go.

Row 1:

THICKENS (Stiffens: anagram of KITCHENS)
REVIEW (analyse: English ditch=REEN, six=VI, gives REVIEN, then left (West) instead of up (North)). Thanks to Clarkey for the final part of this one
HANDED (Helped: Hotel=H, AND, education=ED)
BACK (to sponsor: the rear of something is the back of it)

Row 2:

LINE (railway track: Portuga-LINE-urope)
MASTER (leader: victory=MATE, small=S, real=R (currency))
STEVEN (Spielberg: anagram of EVENTS)
GRAVE (double straight). Solved by Persona

Row 3:

TAPES (piece=PAT, written left=TAP, is in Spanish=ES). Solved by Stiv
TEMPERED (initial letters + PER + bEDs). Solved by aPaulT

PLAN (design: quiet=P, unending street=LANe)
SCOTLAND (S + COT + LAND). Solved by aPaulT

Row 4

DOCK (COCK [pile of hay] with D replacing C). Solved by aPaulT
PARTY (celebrate: or participant gathering, double-straight)
TWIST (TWISTER [swindler], remove ER). Solved by Stiv
FLOW (current: no hesitation in river=FLOWer)

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Part 2: Connections

EVEN: Flow, Tempered, Handed, Steven(s). Solved by aPaulT
YARD: Dock, Scotland, Back, Grave
PLOT: Thickens, Line, Plan, Twist
RAVE: Master, Party, Review, Tapes. Solved by aPaulT

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Part 3: Using the Connections

Arrange the four 4-letter words into a square and read down the columns to reveal four new words. Solved by aPaulT.
PLOT
RAVE
EVEN
YARD

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Part 4: A new wall