Battle men finished in heat (4-2)
I believe the answer is:
warm-up
'heat' is the definition.
(I've seen this before)
'battle men finished' is the wordplay.
I cannot really see how this works, but
'battle' could be 'war' (I've seen this in other clues) and 'war' is present in the answer.
'finished' could be 'up' (eg 'time's up' means the time is finished) and 'up' is present in the answer.
A single letter 'm' remains which might be clued in a way I don't understand.
This may be the basis of clue (or it may be nonsense).
'in' acts as a link.
Can you help me to learn more?
(Other definitions for warm-up that I've seen before include "Exercise before race - reheat food - become more animated" , "Preparatory exercises before an event" , "heat" , "Preliminary exercising" , "Initial exercise period" .)