It's funny how tailless mice hide in that stuff in the cellar (7)
I believe the answer is:
comical
'it's funny' is the definition.
(synonyms)
'tailless mice hide in that stuff in the cellar' is the wordplay.
'tailless' means to remove the last letter (the tail of the word is removed).
'hide in' is an insertion indicator.
'that stuff in the cellar' becomes 'coal' (I am not sure about this - if you are sure you should give a lot more credence to this answer).
'mice' with its last letter taken away is 'mic'.
'mic' inserted within 'coal' is 'COMICAL'.
'how' acts as a link.
Can you help me to learn more?
(Other definitions for comical that I've seen before include "'Amusing, funny (7)'" , "priceless" , "Amusing or droll" , "Causing laughter" , "Rich" .)