Discharge fellows in the NFS (7)
I believe the answer is:
firemen
'the nfs' is the definition.
I can't tell whether this defines the answer.
'discharge fellows' is the wordplay.
'discharge' becomes 'fire' (synonyms).
'fellows' becomes 'men' (fellow can mean a man).
'fire'+'men'='FIREMEN'
'in' is the link.
Can you help me to learn more?
(Other definitions for firemen that I've seen before include "Their job is to extinguish conflagrations" , "Hose wielder" , "They fight conflagrations" , "Stokers" .)