Sustenance to help get me along (4)
I believe the answer is:
meal
'sustenance' is the definition.
(meal is a kind of sustenance)
'get me along' is the wordplay.
'get' is a charade indicator (letters next to each other).
'along' becomes 'al' (I can't justify this - if you can you should believe this answer much more).
'me' next to 'al' is 'MEAL'.
'to help' acts as a link.
Can you help me to learn more?
(Other definitions for meal that I've seen before include "Food for male" , "Repast" , "Eg, lunch" , "Grain ground to powder" , "Food ground up" .)