Motivation beginning to recede in downmarket bar (5)
I believe the answer is:
drive
'motivation' is the definition.
(I've seen this in another clue)
'beginning to recede in downmarket bar' is the wordplay.
'beginning to' indicates taking the first letters.
'in' is an insertion indicator.
'downmarket bar' becomes 'dive' (dive can mean a sleazy bar).
The first letter of 'recede' is 'r'.
'r' going inside 'dive' is 'DRIVE'.
(Other definitions for drive that I've seen before include "Ambition - steer" , "computer store" , "sustained military assault" , "tenacity" , "Operate or control a vehicle" .)