Work to reinforce regular army policy (4)
I believe the answer is:
line
This clue is a quadruple definition!!
'work' is the first definition.
(line can mean someone's profession or work)
'to reinforce' is the second definition.
(lining is a kind of reinforcing)
'regular army' is the third definition.
The answer and definition can be both groups as well as being singular nouns.
Perhaps they are linked in a way I don't understand?
'policy' is the fourth definition.
(as in the party line)
Can you help me to learn more?
(Other definitions for line that I've seen before include "dash one end to the other" , "Railway track; wrinkle" , "Phone connection; queue" , "An American queue" , "short note" .)