Reject some of these grubby desires? (5)
I believe the answer is:
urges
'desires?' is the definition.
'reject some of these grubby' is the wordplay.
'reject' shows that the letters should be reversed in order.
'some of' indicates the answer is hidden within the clue.
'segru' is hidden within 'these grubby'.
'segru' reversed gives 'URGES'.
(Other definitions for urges that I've seen before include "Inner promptings" , "Persuades to do something" , "Strong impulses" , "Presses to do something" , "Compulsions" .)