Soldier on after cutting tail from monster (7)
I believe the answer is:
dragoon
'soldier' is the definition.
(dragoon is a kind of soldier)
'on after cutting tail from monster' is the wordplay.
I cannot quite understand how this works, but
'on' could be 'o' (I've seen this in other clues) and 'o' is located in the answer.
'monster' could be 'dragon' (dragon is a kind of monster) and 'dragon' is found within the remaining letters.
This accounts for all the letters.
This may be the basis of clue (or it may be nonsense).
(Other definitions for dragoon that I've seen before include "Cavalry soldier" , "Harass" , "[CARIBINEER]?" , "Coerce someone to do something against their will" , "Constrain" .)