Note bishop always turning up (5)
I believe the answer is:
breve
'note' is the definition.
(musical note)
'bishop always turning up' is the wordplay.
'bishop' becomes 'B' (abbreviation for bishop in chess).
'always' becomes 'ever' (synonyms).
'turning up' is a reversal indicator.
'ever' written backwards gives 'reve'.
'b'+'reve'='BREVE'
(Other definitions for breve that I've seen before include "Long note (mus.)" , "(In music) long note" , "Accent placed over a vowel" , "Accent - musical note" , "Note equivalent to four minims" .)