Choose not to participate in work followed by racecourse tipster (3,3)
I believe the answer is:
opt out
'choose not' is the definition.
(to opt out of something is to choose not to do it)
'participate in work followed by racecourse tipster' is the wordplay.
I cannot quite understand how this works, but
'work' could be 'op' (common abbreviation for 'opus') and 'op' is found within the answer.
'tipster' could be 'tout' (synonyms) and 'tout' is present in the answer.
No letters remain.
This may be the basis of the clue (or it may be nonsense).
'to' acts as a link.
Can you help me to learn more?
(Other definitions for opt out that I've seen before include "Decline to participate" , "Choose to be excluded" , "'Choose not to take part (3,3)'" , "Choose not to do something" , "Decide not to participate" .)