Very determined man will grass (4-4)
I believe the answer is:
hell-bent
'very determined' is the definition.
'hell bent' can be an answer for 'determined' (I've seen this before). I'm not certain of the 'very' bit.
'man will grass' is the wordplay.
'man will' becomes 'he'll' ('he'll', contraction of 'he will').
'grass' becomes 'bent' (I've seen this before).
'hell'+'bent'='HELL-BENT'
Can you help me to learn more?
(Other definitions for hell-bent that I've seen before include "Determined at all costs" , "Absolutely determined" , "Dead set" , "on path with good intentions" , "Recklessly determined" .)