Stick all fingers and thumbs right into sponge cake (10)
I believe the answer is:
battenberg
'sponge cake' is the definition.
(battenberg is a type of cake)
'stick all fingers and thumbs right' is the wordplay.
'stick' becomes 'bat' (bat is a kind of stick).
'all fingers' becomes 'ten' (complete count).
'and' says to put letters next to each other.
'thumbs right' becomes 'berg' (I am not sure about this - if you are sure you should believe this answer much more).
'bat'+'ten'+'berg'='BATTENBERG'
'into' acts as a link.
(Another definition for battenberg that I've seen is " Marzipan-covered sponge cake".)