This is a charade - where separate parts are joined together in sequence to form the answer word.
Look for a phrase meaning 'if that man is' (2 letters) followed by something that describes 'one drawn to light' (4 letters). The word 'preceding' tells you the order - the first part comes before the second.
Answer: BEHEMOTH | BE HE (if that man is) + MOTH (one drawn to light). A behemoth is indeed something monstrous - a huge creature or thing.