Source of ruin in sight -- not very funny (7)
I believe the answer is:
risible
'funny' is the definition.
(synonyms)
'source of ruin in sight not very' is the wordplay.
'source of ruin' becomes 'r' (I am not sure about this - if you are sure you should give a lot more credence to this answer).
'in sight' becomes 'visible' (similar in meaning).
'not' indicates named letters should be taken away.
'very' becomes 'v' (abbreviation).
'visible' with 'v' taken out is 'isible'.
'r'+'isible'='RISIBLE'
Can you help me to learn more?
(Other definitions for risible that I've seen before include "Laughter-provoking" , "Laughable, amusing" , "Farcical" , "Comical, laughable" , "Ludicrous, laughable" .)