Point of advert by Nationalist and Conservative (10)
I believe the answer is:
promontory
'point' is the definition.
(I've seen this before)
'advert by nationalist and conservative' is the wordplay.
'advert by' becomes 'promo' (I am not sure about this - if you are sure you should give a lot more credence to this answer).
'nationalist' becomes 'n' (abbreviation in politics).
'and' means one lot of letters go next to another.
'conservative' becomes 'tory' (informal term for a Conservative Party member).
'promo'+'n'+'tory'='PROMONTORY'
'of' is the link.
Can you help me to learn more?
(Other definitions for promontory that I've seen before include "Bluff" , "Headland" , "Bill" , "Point" , "Coastal feature" .)