Under bent elbow (5)
I believe the answer is:
below
'under' is the definition.
(synonyms)
'bent elbow' is the wordplay.
'bent' indicates an anagram.
'elbow' is an anagram of 'BELOW'.
(Other definitions for below that I've seen before include "Inferior" , "Feel miserable" , "Later in text" , "Not worthy of" , "Beneath" .)