Turn up at start of the finale (6)
I believe the answer is:
attend
'turn up' is the definition.
(thesaurus)
'at start of the finale' is the wordplay.
'start of' suggests taking the first letters.
'finale' becomes 'end' (I've seen this before).
The initial letter of 'the' is 't'.
'at'+'t'+'end'='ATTEND'
(Other definitions for attend that I've seen before include "Be present at, turn up" , "Watch" , "chaperon" , "take heed" , "Listen carefully" .)