Suspicion at first about tenor's singing style (4)
I believe the answer is:
scat
'singing style' is the definition.
(I've seen this in another clue)
'suspicion at first about tenor's' is the wordplay.
'at first' suggests taking the first letters.
'about' becomes 'ca' (abbreviation for 'circa').
'tenor' becomes 't'.
The first letter of 'suspicion' is 's'.
's'+'ca'+'t'='SCAT'
(Other definitions for scat that I've seen before include "Animal droppings - small silvery fish" , "Style of jazz singing" , "Bolt" , "it's dropped by 21 [SNAKES]" , "Get away with cats" .)