Bust unionist leadership in the province (6)
I believe the answer is:
statue
'bust' is the definition.
(type of statue)
'unionist leadership in the province' is the wordplay.
'leadership' indicates taking the first letters.
'in the' means one lot of letters goes inside another.
'province' becomes 'state' (synonyms).
The initial letter of 'unionist' is 'u'.
'u' placed within 'state' is 'STATUE'.
(Other definitions for statue that I've seen before include "Figurative sculpture" , "Modelled figure of a human or animal" , "A carved or sculpted figure" , "Carved likeness" , "Solid representation of the human form" .)