Drunk man is flexible (5)
I believe the answer is:
lithe
'flexible' is the definition.
(I've seen this before)
'drunk man' is the wordplay.
'drunk' becomes 'lit' (I've seen this in another clue).
'man' becomes 'he' (he refers to a man).
'lit'+'he'='LITHE'
'is' is the link.
(Other definitions for lithe that I've seen before include "Physically supple, agile" , "Don -, opera by Verdi" , "grace" , "Supple and limber" , "Slender, supple" .)