Bar put up outside a show (6)
I believe the answer is:
reveal
'show' is the definition.
(I know that reveal is a more specific form of the action show)
'bar put up outside a' is the wordplay.
I cannot quite see how this works, but
'a' is within the answer.
The remaining letters 'revel' is a valid word which might be clued in a way I don't see.
This explanation may well be incorrect...
Can you help me to learn more?
(Other definitions for reveal that I've seen before include "Make public" , "Leaver (anag.)" , "Uncover or expose" , "Expose or display" , "Make known to others" .)