Turn back and half resist the monsters (5)
I believe the answer is:
ogres
'the monsters' is the definition.
('ogre' can be a synonym of 'monster')
'turn back and half resist' is the wordplay.
'turn' becomes 'go' (a person's move in a board game**).
'back' shows that the letters should be reversed in order.
'and' means one lot of letters go next to another.
'half' indicates taking half.
'go' reversed gives 'og'.
'resist' halved is 'res'.
'og'+'res'='OGRES'
(Other definitions for ogres that I've seen before include "Terrifying types" , "Monstrous giants and man-eaters" , "Giant types" , "Man-eating giants of folklore" , "Monsters can be goers" .)