Reduced charge cheers up setter's mood (10)
I believe the answer is:
indicative
'mood' is the definition.
(indicative is a kind of mood)
'reduced charge cheers up setter's' is the wordplay.
'reduced' means to remove the last letter.
'charge' becomes 'indict' (indicting is a kind of charging).
'cheers up' becomes 'at' (I've seen this in other clues).
'setter's' becomes 'ive' (I've seen this in other clues**).
'indict' with its final letter removed is 'indic'.
'indic'+'at'+'ive'='INDICATIVE'
(Other definitions for indicative that I've seen before include "Serving as a sign" , "mood" .)