Explosive is prime requirement for the robbery (5)
I believe the answer is:
heist
'robbery' is the definition.
(I know that heist is a type of robbery)
'explosive is prime requirement for the' is the wordplay.
'explosive' becomes 'he' (abbreviation for high explosive).
'prime requirement for' says to take the initial letters (the first or prime letter required by the word).
The first letter of 'the' is 't'.
'he'+'is'+'t'='HEIST'
(Other definitions for heist that I've seen before include "Bank robbery" , "crime?" , "Audacious robbery" , "Robbery, often at gunpoint" , "Armed robbery" .)