I like this drink which may be radioactive (7)
I believe the answer is:
isotope
'may be radioactive' is the definition.
(I've seen this before)
'i like this drink' is the wordplay.
'like this' becomes 'so' ('like so').
'drink' becomes 'tope' (synonyms).
'i'+'so'+'tope'='ISOTOPE'
'which' is the link.
(Other definitions for isotope that I've seen before include "Variant of a particular chemical element -- ie stoop (anag)" , "O, is poet a species of atom?" , "Type of atom, maybe radioactive" , "Oo, spite! (anag.)" , "Form of atomic nucleus" .)