Poet in pub, Duke's Head (4)
I believe the answer is:
bard
'poet' is the definition.
(I've seen this before)
'pub duke's head' is the wordplay.
'pub' becomes 'bar' (I've seen this before).
'head' says to take the initial letters.
The initial letter of 'dukes' is 'd'.
'bar'+'d'='BARD'
'in' is the link.
(Other definitions for bard that I've seen before include "Eisteddfod winner" , "Animal; cruel person" , "A lyric poet" , "Ancient poet" , "A drab sort of old poet" .)