Explosive rhythm section better (10,3)
I believe the answer is:
percussion cap
'explosive' is the definition.
(I know that percussion cap is a type of cap)
'rhythm section better' is the wordplay.
I cannot quite see how this works, but
'section' could be 'percussion' (I have seen 'Section of orchestra' mean 'percussion' so perhaps 'section' could also mean 'percussion') and 'percussion' is found in the answer.
'better' could be 'cap' (both can mean to beat somebody else's attempt) and 'cap' is located in the answer.
This accounts for all the letters.
This explanation may well be incorrect...
Can you help me to learn more?
(Other definitions for percussion cap that I've seen before include "Explosive device detonated by striking" , "banger" , "Explosive for toy guns" , "child's report" , "Something exploded by striking" .)