Soldiers, on reflection, will be found among the fit (5)
I believe the answer is:
throe
'fit' is the definition.
(I've seen this in another clue)
'soldiers on reflection will be found among the' is the wordplay.
'soldiers on reflection will' becomes 'ro' (I can't justify this - if you can you should give a lot more credence to this answer).
'be found among' indicates putting letters inside.
'ro' inserted into 'the' is 'THROE'.
Can you help me to learn more?
(Other definitions for throe that I've seen before include "Convulsion" , "Other (anag.)" , "pain" , "Spasm - pang" .)