Beat time in a trance (4)
I believe the answer is:
rapt
'in a trance' is the definition.
(I've seen this in another clue)
'beat time' is the wordplay.
'beat' becomes 'rap' (both can mean to knock or hit).
'time' becomes 't' (abbreviation).
'rap'+'t'='RAPT'
(Other definitions for rapt that I've seen before include "Completely absorbed" , "'Transported, entranced (4)'" , "Held spellbound" , "riveted" , "Ecstatic in part" .)