Son ready for heavy drinking (8)
I believe the answer is:
swilling
'heavy drinking' is the definition.
(swill can mean to drink large quantities)
'son ready' is the wordplay.
'son' becomes 's'.
'ready' becomes 'willing' (ready can mean available or willing).
's'+'willing'='SWILLING'
'for' acts as a link.
(Other definitions for swilling that I've seen before include "Drinking greedily" , "drinking large amount" .)