Novel's pathetic protagonist losing ring but winning old cash (13)
I believe the answer is:
trainspotting
'novel's' is the definition.
(Irvine Welsh novel)
'pathetic protagonist losing ring but winning old cash' is the wordplay.
'pathetic' is an anagram indicator (a pathetically bad ordering of the letters).
'losing' is a deletion indicator.
'ring' becomes 'o' (letter resembling a ring).
'but winning' means one lot of letters goes inside another (inserted letters are acquired or won by the word).
'old cash' becomes 'tin' (old-fashioned slang term for money).
'protagonist' with 'o' removed is 'prtagonist'.
'prtagonist' anagrammed gives 'trainspotg'.
'trainspotg' going around 'tin' is 'TRAINSPOTTING'.
(Other definitions for trainspotting that I've seen before include "Film about drug addicts (or railway buffs?)" , "1996 film based on a novel by Irvine Welsh" , "hobby" .)