Potential spies lob explosive (8)
I believe the answer is:
possible
'potential' is the definition.
(I know that potential can be written as possible)
'spies lob explosive' is the wordplay.
'explosive' indicates anagramming the letters.
'spies'+'lob'='spieslob'
'spieslob' is an anagram of 'POSSIBLE'.
(Other definitions for possible that I've seen before include "Conceivable, imaginable" , "Capable of being achieved" , "Capable of happening" , "Achievable, able to be done" , "Conceivable, practicable" .)