What one who neglects to take his fare will do (6)
I believe the answer is:
starve
'fare will do' is the definition.
'starve' can be an answer for 'fare' (I have seen 'Lack food ' mean 'starve' so perhaps 'food' could also mean 'starve'). I'm not certain of the 'will do' bit.
I can't explain the rest of the clue.
Can you help me to learn more?
(Other definitions for starve that I've seen before include "Deprive of food" , "Become famished" , "Averts (anag)" , "Deprive of sustenance" , "Suffer from want of food" .)