Soldiers can make sport out of love! (6)
I believe the answer is:
troops
'soldiers' is the definition.
(groups of soldiers)
'make sport out of love' is the wordplay.
'make' is an anagram indicator.
'out of' indicates putting letters inside (some letters on the outside of others).
'love' becomes 'o' (love means zero in tennis).
'sport' is an anagram of 'trops'.
'trops' placed around 'o' is 'TROOPS'.
'can' acts as a link.
(Other definitions for troops that I've seen before include "Army" , "Military divisions" , "men" , "Groups of soldiers" , "Cavalry" .)