Unyielding soldier breaking free (5)
I believe the answer is:
rigid
'unyielding' is the definition.
(I've seen this before)
'soldier breaking free' is the wordplay.
'soldier' becomes 'GI' (GI can mean a US soldier).
'breaking' indicates putting letters inside.
'free' becomes 'rid' (to be free of something is to be rid of it).
'gi' placed within 'rid' is 'RIGID'.
(Other definitions for rigid that I've seen before include "Frozen" , "Uncompromising" , "Stiff, unmoving" , "unwilling to move" , "Incapable of or resistant to bending" .)