Timid type eating second sweet (6)
I believe the answer is:
mousse
'sweet' is the definition.
(mousse is a kind of sweet)
'timid type eating second' is the wordplay.
'timid type' becomes 'mouse' (I've seen this before).
'eating' means one lot of letters goes inside another.
'second' becomes 's' (common abbreviation).
'mouse' going around 's' is 'MOUSSE'.
(Other definitions for mousse that I've seen before include "A dessert, or creamy substance used to style hair" , "Light creamy dessert, set with gelatin" , "Gel" , "Frothy creamy substance for styling hair" , "Creamy dish" .)