Note skin damage — it's huge, man! (5)
I believe the answer is:
titan
'note skin' is the definition.
Although both the answer and definition are singular nouns, I don't understand how they can define each other.
'damage it's huge man' is the wordplay.
'damage' indicates an anagram (I've seen this in other clues).
'huge man' becomes 'tan' (I am not sure about the 'huge' bit.).
'it' with letters rearranged gives 'ti'.
'ti'+'tan'='TITAN'
Can you help me to learn more?
(Other definitions for titan that I've seen before include "colossal one" , "Moon of Saturn visited by the Huygens probe" , "Atlas, possibly" , "Taint (anag.)" , "enormous thing" .)