Resolve to come good and exercise (7)
I believe the answer is:
workout
'resolve' is the definition.
Although both the answer and definition are singular nouns, I cannot see how one could define the other.
'come good and exercise' is the wordplay.
'come good' becomes 'out' (I can't explain this - if you can you should give a lot more credence to this answer).
'and' means one lot of letters go next to another.
'exercise' becomes 'work' (synonyms).
'out' after 'work' is 'WORKOUT'.
'to' is the link.
Can you help me to learn more?
(Other definitions for workout that I've seen before include "Vigorous exercise session" , "Bout of exercise in gym" , "A session of physical exercise" , "Vigorous PE session" , "gym session?" .)