Portion of rarebit; a style of savoury (5)
I believe the answer is:
'savoury' is the definition.
'portion of rarebit a style' is the wordplay.
'portion of' says the answer is hidden in the clue.
'TASTY' is hidden in the letters of 'rarebit a style'.
'of' is the link.
(Other definitions for tasty that I've seen before include "Pleasant to savour" , "Pleasantly flavoursome" , "Like nice grub" , "Pleasantly flavoured" , "With a nice flavour" .)