Timid chap taking extra small dessert (6)
I believe the answer is:
mousse
'dessert' is the definition.
(mousse is a kind of dessert)
I don't understand how the remainder of the clue works.
Can you help me to learn more?
(Other definitions for mousse that I've seen before include "Something for the hair" , "Light creamy dessert, set with gelatin" , "Creamy dessert; hair dressing" , "Gel" , "F" .)