Secure Wahlberg, say, for feature (8)
I believe the answer is:
landmark
'for feature' is the definition.
(I've seen this before)
'secure wahlberg' is the wordplay.
'secure' becomes 'land' (I've seen this in other clues).
'wahlberg' becomes 'mark' (I can't explain this - if you can you should give a lot more credence to this answer).
'land'+'mark'='LANDMARK'
'say' acts as a link.
Can you help me to learn more?
(Other definitions for landmark that I've seen before include "Durham Cathedral, say" , "Conspicuous feature" , "historic event" , "Shard, for example" , "of great significance" .)