Cooking a bannock finally in Crosby (6)
I believe the answer is:
baking
'cooking' is the definition.
(baking is a kind of cooking)
'a bannock finally in crosby' is the wordplay.
'finally' says to take the final letters.
'in' indicates putting letters inside.
'crosby' becomes 'bing' (singer Bing Crosby).
The final letter of 'bannock' is 'k'.
'a'+'k'='ak'
'ak' going inside 'bing' is 'BAKING'.
(Other definitions for baking that I've seen before include "Making bread, cake or pastry" , "For putting bun in the oven" , "Very hot (in the kitchen?)" , "Cooking by dry heat" , "Extremely hot" .)