Spots politician passing through stately homes (7)
I believe the answer is:
pimples
'spots' is the definition.
(I've seen this before)
'politician passing through stately homes' is the wordplay.
'politician' becomes 'MP' (Member of Parliament).
'passing through' is an insertion indicator.
'stately homes' becomes 'piles' (I can't justify this - if you can you should give a lot more credence to this answer).
'mp' going inside 'piles' is 'PIMPLES'.
Can you help me to learn more?
(Other definitions for pimples that I've seen before include "Small unsightly pustules on face" , "(Skin) spots" , "Rash" .)