About to tuck into sourdough! (5)
I believe the answer is:
bread
'about to tuck into sourdough' is the definition.
I can't tell whether this defines the answer.
'about to tuck into sourdough' is the wordplay.
'about' becomes 'rea' (I've seen this in other clues).
'to tuck into' indicates putting letters inside.
'sourdough' becomes 'bd' (I can't justify this - if you can you should believe this answer much more).
'rea' going into 'bd' is 'BREAD'.
(Other definitions for bread that I've seen before include "It may be made from meal" , "Dosh (slang)" , "Dosh - a bloomer, perhaps?" , "Staple food" , "brass" .)