Twain hero, beset by drink, is to give in (5,2)

'to give in' is the definition.
I know nothing about this answer so I cannot judge whether it can be defined by this definition.

'twain hero beset by drink' is the wordplay.
'twain hero' becomes 'huck' (I've seen this in another clue).
'beset by' indicates putting letters inside ('beset' could historically mean 'cover').
'drink' becomes 'cup' (a cup of drink).
'huck' going into 'cup' is 'CHUCK UP'.

'is' is the link.

Can you help me to learn more?