Men to go back, always ending in retreat (4)
I believe the answer is:
nook
'retreat' is the definition.
(I know that nook is a type of retreat)
'men to go back always ending' is the wordplay.
'back' says to take the final letters (the letter at the back).
'always' becomes 'k' (I am not sure about this - if you are sure you should believe this answer much more).
'ending' says to put letters next to each other.
The last letters of 'men to go' are 'noo'.
'noo'+'k'='NOOK'
'in' acts as a link.
Can you help me to learn more?
(Other definitions for nook that I've seen before include "Cubbyhole" , "Cosy corner" , "Secluded recess" , "Sheltered corner" , "Small space" .)