Welcome letter contains something tasty (8)
I believe the answer is:
omelette
'something tasty' is the definition.
(I've seen this before)
'welcome letter contains' is the wordplay.
'contains' indicates a hidden word.
'OMELETTE' can be found hidden inside 'welcome letter'.
(Other definitions for omelette that I've seen before include "breakfast" , "Food dish (that can't be made without breaking eggs)" , "Simple egg dish" , "Beaten-egg dish" , "One getting beaten" .)