It's funny, a gas, millions seen on TV (6)
I believe the answer is:
sitcom
'on tv' is the definition.
The definition and answer can be both related to communication as well as being singular nouns.
Maybe there's a link between them I don't understand?
'it's funny a gas millions' is the wordplay.
'funny' indicates an anagram.
'a gas' becomes 'co' (CO is carbon monoxide).
'millions' becomes 'm' (abbreviation).
'its' with letters rearranged gives 'sit'.
'sit'+'co'+'m'='SITCOM'
'seen' acts as a link.
Can you help me to learn more?
(Other definitions for sitcom that I've seen before include "Bread, perhaps" , "Amusing TV genre" , "Shortened form of situation comedy" , "'Humorous drama based on situations, in short (6)'" , "Episodical TV programme" .)