Tough soldiers, retreating Roman men (7)
I believe the answer is:
signori
'roman men' is the definition.
(plural of 'signor', 'Mr' in Italian and so Rome)
'tough soldiers retreating' is the wordplay.
'tough' becomes 'iron'.
'soldiers' becomes 'gis' (I've seen this in other clues**).
'retreating' says the letters should be written backwards.
'iron'+'gis'='irongis'
'irongis' back-to-front is 'SIGNORI'.
(Other definitions for signori that I've seen before include "men of Roman stamp?" , "Italian men" , "Italians" , "Italian gents" .)