Former lead in Hamlet, one with part in show (7)
I believe the answer is:
exhibit
'show' is the definition.
(exhibit is a kind of show)
'former lead in hamlet one with part' is the wordplay.
'former' becomes 'ex' (prefix meaning former or onetime).
'lead in' suggests taking the first letters.
'one' becomes 'i' (Roman numeral).
'with' means one lot of letters go next to another.
'part' becomes 'bit' (both mean a piece of something).
The initial letter of 'hamlet' is 'h'.
'ex'+'h'+'i'+'bit'='EXHIBIT'
'in' is the link.
(Other definitions for exhibit that I've seen before include "Something on show" , "Show - piece of evidence in court" , "Object on formal public display" , "Give public show, as of paintings" , "Manifest" .)