Thanks to you, toppings are delicious (5)
I believe the answer is:
tasty
'delicious' is the definition.
(I've seen this in another clue)
'thanks to you toppings' is the wordplay.
'thanks' becomes 'ta' (UK informal version of 'thank you').
'to you toppings' becomes 'sty' (I can't explain this - if you can you should give a lot more credence to this answer).
'ta'+'sty'='TASTY'
'are' is the link.
Can you help me to learn more?
(Other definitions for tasty that I've seen before include "Mouth-watering" , "Toothsome" , "Pleasantly flavoured" , "Like nice grub" , "Appetising, having pleasant flavour" .)