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