Soldiers carrying much less mass, for instance (4,2)
I believe the answer is:
such as
'for instance' is the definition.
(I've seen this in another clue)
'soldiers carrying much less mass' is the wordplay.
'soldiers' becomes 'sas' (Special Air Service).
'carrying' is an insertion indicator.
'less' suggests deleting specific letters (less can mean minus).
'mass' becomes 'm' (symbol used in Physics e.g. f=ma).
'much' with 'm' removed is 'uch'.
'sas' enclosing 'uch' is 'SUCH AS'.
(Other definitions for such as that I've seen before include "For example" , "Like" .)