One helping a non-drinker to crack open something unlikely (7)
I believe the answer is:
abetter
'one helping' is the definition.
The answer is a person as well as being a singular noun. This is suggested by the definition.
'a non-drinker to crack open something unlikely' is the wordplay.
'non drinker' becomes 'tt' (abbreviation for teetotaller).
'to crack open' means one lot of letters goes inside another (inserted letters crack into the word).
'something unlikely' becomes 'beer' (I can't justify this - if you can you should believe this answer much more).
'tt' going inside 'beer' is 'better'.
'a'+'better'='ABETTER'
Can you help me to learn more?
(Other definitions for abetter that I've seen before include "who gives encouragement?" , "one who helps in a crime" , "Supporter" , "Partner in crime; tree bat (anag.)" , "who may support criminal activity?" .)