Mary goes around with soldiers (4)
I believe the answer is:
army
'soldiers' is the definition.
(group of soldiers)
'mary goes around' is the wordplay.
'goes around' indicates an anagram.
'mary' with letters rearranged gives 'ARMY'.
'with' acts as a link.
(Other definitions for army that I've seen before include "A defence force" , "fighters" , "Ground forces" , "Organisation for soldiering" , "Large military force" .)