Soldiers caught a monster (3)
I believe the answer is:
orc
'a monster' is the definition.
(I've seen this before)
'soldiers caught' is the wordplay.
'soldiers' becomes 'or' (Other Rank**).
'caught' becomes 'c' (cricket abbreviation).
'or'+'c'='ORC'
(Other definitions for orc that I've seen before include "Tolkienian monster" , "Tolkien ogre" , "Fierce goblin" , "Giant" , "Ugly creature" .)