Outline of tap? (8)
I believe the answer is:
abstract
'outline' is the definition.
(synonyms)
'tap?' is the wordplay.
I cannot really understand how this works, but
'tap?' could be 'act' (tap is a kind of act) and 'act' is found in the answer.
This may be the basis of the clue (or it may be nonsense).
'of' is the link.
Can you help me to learn more?
(Other definitions for abstract that I've seen before include "Academic" , "piece of artwork" , "Theoretical; abstruse" , "Summary; remove" , "Appropriate - theoretical - summary" .)