Cup of tea left to go cold (7)
I believe the answer is:
chalice
'cup' is the definition.
(chalice is a kind of cup)
'tea left to go cold' is the wordplay.
'tea' becomes 'cha' (cha is a type of tea).
'left' becomes 'l' (common abbreviation).
'to' means one lot of letters go next to another.
'go cold' becomes 'ice' (I've seen this before. I am not sure about the 'go' bit.).
'cha'+'l'+'ice'='CHALICE'
'of' acts as a link.
Can you help me to learn more?
(Other definitions for chalice that I've seen before include "Church wine cup" , "bowl" , "Cup used in church" , "Large goblet for consecrated wine" , "Church vessel" .)