Listeners in nuclear submarine? (4)
I believe the answer is:
ears
'listeners' is the definition.
(body parts which listen)
'in nuclear submarine?' is the wordplay.
'in' indicates the answer is hidden within the clue.
'EARS' can be found hidden inside 'nuclear submarine'.
(Other definitions for ears that I've seen before include "Seed-bearing parts of corn" , "Heads of corn" , "''He who has ... to hear, let him hear'' (bible)" , "Spikes of corn" , "Sear (anag.)" .)