Turn pale making an entreaty (4)
I believe the answer is:
plea
'an entreaty' is the definition.
(I know that plea is a type of entreaty)
'turn pale' is the wordplay.
'turn' indicates an anagram.
'pale' anagrammed gives 'PLEA'.
'making' acts as a link.
(Other definitions for plea that I've seen before include "Urgent entreaty" , "Earnest entreaty" , "Heartfelt request" , "Dispute" , "Excuse - pretext" .)