Crooked stamp on, he delivers (7)
I believe the answer is:
postman
'he delivers' is the definition.
(a postman delivers letters)
'crooked stamp on' is the wordplay.
'crooked' is an anagram indicator.
'stamp'+'on'='stampon'
'stampon' is an anagram of 'POSTMAN'.
(Other definitions for postman that I've seen before include "TV's Pat, for instance" , "Male mail carrier" , "Chap with letters" , "Mail deliverer" , "Male to deliver mail" .)