A request certain to give satisfaction (8)
I believe the answer is:
pleasure
'satisfaction' is the definition.
(I've seen this in another clue)
'a request certain' is the wordplay.
'a request' becomes 'plea' (plea is a kind of request).
'certain' becomes 'sure' (synonyms).
'plea'+'sure'='PLEASURE'
'to give' is the link.
(Other definitions for pleasure that I've seen before include "Delectation, delight" , "Delight, joy" , "Enjoyment, happiness" , "A very desirable feeling" , "Gratification of the senses" .)