Hideous building has one seeing red (7)
I believe the answer is:
eyesore
'hideous building' is the definition.
(I've seen this before)
'one seeing red' is the wordplay.
'one' becomes 'eye' (I can't explain this - if you can you should give a lot more credence to this answer).
'seeing red' becomes 'sore' (I've seen this in another clue).
'eye'+'sore'='EYESORE'
'has' is the link.
Can you help me to learn more?
(Other definitions for eyesore that I've seen before include "it looks bad" , "something one wouldn't want to see" , "Hideous sight" , "pigsty" , "It's offensively ugly" .)