Ate bun doubtfully during golf club spread (6,6)
I believe the answer is:
peanut butter
'spread' is the definition.
(I know that Peanut butter is a type of spread)
'ate bun doubtfully during golf club' is the wordplay.
'doubtfully' indicates an anagram.
'during' is an insertion indicator.
'golf club' becomes 'putter' (I've seen this before).
'ate'+'bun'='atebun'
'atebun' with letters rearranged gives 'eanutb'.
'eanutb' going inside 'putter' is 'PEANUT BUTTER'.
(Other definitions for peanut butter that I've seen before include "Spread made from groundnuts" , "Golden brown paste" , "Leguminous spread" , "something to eat" .)