Drink leads to ruin amongst wayward Wrens (9)
I believe the answer is:
sundowner
'drink' is the definition.
(I've seen this before)
'ruin amongst wayward wrens' is the wordplay.
'ruin' becomes 'undo' (I've seen this before**).
'amongst' means one lot of letters goes inside another (I've seen this in other clues).
'wayward' indicates anagramming the letters.
'wrens' with letters rearranged gives 'swner'.
'undo' placed within 'swner' is 'SUNDOWNER'.
'leads to' is the link.
(Other definitions for sundowner that I've seen before include "Evening drink" , "cocktail?" , "Twilight drink" , "Victorian tramp?" , "drink after work?" .)