Pale sort of request (4)
I believe the answer is:
plea
'request' is the definition.
(plea is a kind of request)
'pale sort' is the wordplay.
'sort' is an anagram indicator.
'pale' is an anagram of 'PLEA'.
'of' is the link.
(Other definitions for plea that I've seen before include "Guilty perhaps" , "Excuse - pretext" , "suit" , "Leap (anag.)" , "Appeal - with bargaining?" .)