He works on the side to get better results (7)
I believe the answer is:
trainer
'better results' is the definition.
The answer and definition can be both people as well as being singular nouns.
Perhaps you can see an association between them that I can't see?
'he works on the side to get' is the wordplay.
'he works' becomes 'tra' (I can't explain this - if you can you should believe this answer much more).
'on the side' says to hollow out the word (remove centre letters) (the letters on the sides).
'to get' becomes 'infer' (inferring is a kind of getting).
'infer' with its middle removed is 'iner'.
'tra'+'iner'='TRAINER'
Can you help me to learn more?
(Other definitions for trainer that I've seen before include "As a P.E. instructor" , "Casual shoe" , "The odd thing an athlete may leave behind" , "Coach - one of a pair of shoes?" , "Soft shoe; simulator" .)