It entails taking men on board, ending with mate (5)
I believe the answer is:
chess
'mate' is the definition.
The definition and answer can be both plants as well as being singular nouns.
I also know that 'mate' relates to this answer.
'it entails taking men on board ending' is the wordplay.
I cannot really see how this works, but
'it' could be 'e' ('e' can mean 'electronic' which is similar to 'IT') and 'e' is present in the answer.
'board' could be 'ss' (I've seen this in other clues) and 'ss' is located in the answer.
The remaining letters 'ch' is a valid word which might be clued in a way I don't see.
This explanation may well be incorrect...
'with' acts as a link.
(Other definitions for chess that I've seen before include "that has over thirty men on board" , "form of battle" , "Game with kings and queens" , "show" , "A game of skill" .)