Bring in each one of the Armed Forces (4)
I believe the answer is:
earn
'bring in' is the definition.
(as in bringing in money)
'each one of the armed forces' is the wordplay.
'each' becomes 'ea' (abbreviation).
'one of the armed forces' becomes 'rn' (I can't justify this - if you can you should give a lot more credence to this answer).
'ea'+'rn'='EARN'
Can you help me to learn more?
(Other definitions for earn that I've seen before include "make bread?" , "Near (anag.)" , "Win" , "Take home" , "Make - merit" .)