He caught poachers like little Dennis after the war (6)
I believe the answer is:
warden
'he caught poachers' is the definition.
The answer is a person as well as being a singular noun. This is suggested by the definition.
'little dennis after the war' is the wordplay.
'little dennis' becomes 'den' (I am not sure about this - if you are sure you should give a lot more credence to this answer).
'after' is a charade indicator (letters next to each other).
'den' after 'war' is 'WARDEN'.
'like' is the link.
Can you help me to learn more?
(Other definitions for warden that I've seen before include "The - (Trollope)" , "Prison or traffic official" , "Head of certain schools, colleges, etc" , "Official with supervisory duties, as in relation to a church" , "College head" .)