Cheerful conductor indicates this (6)
I believe the answer is:
upbeat
This clue is a double definition.
'cheerful' is the first definition.
(I know that cheerful can be written as upbeat)
'conductor indicates this' is the second definition.
(as in a musical upbeat)
(Other definitions for upbeat that I've seen before include "Conductor's beginning" , "Promising" , "Of mood, cheerful and optimistic" , "Cheerfully optimistic" , "in every bar" .)