Shy and stupid to object to returning (5)
I believe the answer is:
timid
'shy' is the definition.
('timid' can be a synonym of 'shy')
'stupid to object to returning' is the wordplay.
'stupid' becomes 'dim' (I've seen this before).
'to object' becomes 'it' (pronoun for an inanimate object).
'to returning' says the letters should be written in reverse.
'dim'+'it'='dimit'
'dimit' in reverse letter order is 'TIMID'.
'and' is the link.
(Other definitions for timid that I've seen before include "Not assertive, retiring" , "Fearful - shy" , "Diffident, faint-hearted" , "Lacking in courage" , "not forward" .)