Cheerful substitute, good, honourable (10)
I believe the answer is:
upstanding
'honourable' is the definition.
(similar in meaning)
'cheerful substitute good' is the wordplay.
'cheerful' becomes 'up' (up can mean cheerful or upbeat).
'substitute' becomes 'stand in' (synonyms).
'good' becomes 'g' (abbreviation).
'up'+'standin'+'g'='UPSTANDING'
(Other definitions for upstanding that I've seen before include "Honest, respectable; erect" , "Ready for toast" , "as we must be when the judge appears!" .)