Awful lot to be imbibed by Robin Goodfellow? Whatever's available! (3,4)
I believe the answer is:
pot luck
'whatever's available' is the definition.
(random selection)
'awful lot to be imbibed by robin goodfellow?' is the wordplay.
'awful' indicates anagramming the letters.
'to be imbibed by' means one lot of letters goes inside another.
'robin goodfellow?' becomes 'puck' (character from A Midsummer Night's Dream).
'lot' is an anagram of 'otl'.
'otl' put within 'puck' is 'POT-LUCK'.
(Other definitions for pot luck that I've seen before include "Sheer chance" , "Whatever may happen to be available" .)