Pale sort of petition (4)
I believe the answer is:
plea
'petition' is the definition.
(I've seen this before)
'pale sort' is the wordplay.
'sort' indicates an anagram.
'pale' with letters rearranged gives 'PLEA'.
'of' is the link.
(Other definitions for plea that I've seen before include "suit" , "Dispute" , "Earnest entreaty" , "Guilty perhaps" , "Appeal - with bargaining?" .)