Airborne troop starts to intercept the enemy drone (8)
I believe the answer is:
parasite
'drone' is the definition.
(thesaurus)
'airborne troop starts to intercept the enemy' is the wordplay.
'airborne troop' becomes 'paras' (paratroopers).
'starts to' says to take the initial letters.
The initial letters of 'intercept the enemy' is 'ite'.
'paras'+'ite'='PARASITE'
(Other definitions for parasite that I've seen before include "Organism living off another" , "it sucks blood" , "one who thrives on (or off) another" , "Animal that feeds off another" , "unwanted guest" .)