Additional pay for a sincere sort (8)
I believe the answer is:
'additional pay' is the definition.
Although both the answer and definition are singular nouns, I don't see how one could define the other.
'a sincere sort' is the wordplay.
'sort' indicates an anagram.
'asincere' anagrammed gives 'INCREASE'.
'for' is the link.
Can you help me to learn more?
(Other definitions for increase that I've seen before include "step up" , "Grow bigger" , "boost" , "extra money at work" , "Become bigger or greater in amount" .)