Very small amount of dessert (6)
I believe the answer is:
trifle
'dessert' is the definition.
(I know that trifle is a type of dessert)
'very small amount' is the wordplay.
'very' becomes 't' (I can't justify this - if you can you should give a lot more credence to this answer).
'small amount' becomes 'rifle' (I've seen this in another clue).
't'+'rifle'='TRIFLE'
'of' acts as a link.
Can you help me to learn more?
(Other definitions for trifle that I've seen before include "Pudding - bagatelle" , "Triviality" , "Treat frivolously" , "one's last course" , "Insignificant thing" .)