Prime Minister has sex appeal in part (4)
I believe the answer is:
pitt
'prime minister' is the definition.
(I've seen this before)
'sex appeal in part' is the wordplay.
'sex appeal' becomes 'it'.
'in' indicates putting letters inside.
'part' becomes 'pt' (abbreviation).
'it' placed into 'pt' is 'PITT'.
'has' is the link.
(Other definitions for pitt that I've seen before include "William --, who became Prime Minister at 24" , "old politician" , "Old British statesman" , "a name in politics once" , "William --, early PM" .)