Musicians in clubs boom terribly (5)
I believe the answer is:
combo
'musicians' is the definition.
(I've seen this before)
'clubs boom terribly' is the wordplay.
'clubs' becomes 'c' (abbreviation used in card games such as bridge).
'terribly' indicates anagramming the letters.
'boom' with letters rearranged gives 'ombo'.
'c'+'ombo'='COMBO'
'in' acts as a link.
(Other definitions for combo that I've seen before include "Small jazz group" , "group of players" , "musicians" , "Small pop group" , "Small jazz or dance band" .)