Wild deer, having had nothing to eat, will eat away (5)
I believe the answer is:
erode
'eat away' is the definition.
(synonyms)
'wild deer having had nothing to eat' is the wordplay.
'wild deer' becomes 'ere' (I can't justify this - if you can you should believe this answer much more).
'having' is an insertion indicator.
'had' becomes 'd' (in contractions e.g. 'I'd', 'you'd' etc).
'nothing' becomes 'O' (looks like zero - 0).
'to eat' means one lot of letters goes inside another.
'ere' enclosing 'd' is 'erde'.
'erde' enclosing 'o' is 'ERODE'.
'will' acts as a link.
Can you help me to learn more?
(Other definitions for erode that I've seen before include "go to pieces!" , "Gradually wear away" , "Eat away" , "Wear away with weather" , "Grind down" .)