Rubbish found by soldiers in part of a helicopter (5)
I believe the answer is:
rotor
'part of a helicopter' is the definition.
(I know that rotor is part of chopper)
'rubbish found by soldiers' is the wordplay.
'rubbish' becomes 'rot' (both can mean nonsense).
'found by' says to put letters next to each other.
'soldiers' becomes 'OR' (Other Ranks).
'rot'+'or'='ROTOR'
'in' acts as a link.
(Other definitions for rotor that I've seen before include "Revolving component" , "I go round" , "Part of electric motor" , "Part of, eg, a motor" , "device for lifting a chopper" .)