Ghastly building the writer spotted in broadcast (7)
I believe the answer is:
eyesore
'ghastly building' is the definition.
'eyesore' can be an answer for 'building' (I have seen 'Ugly building ' mean 'eyesore' so perhaps 'building' could also mean 'eyesore'). I am not sure about the 'ghastly' bit.
'writer spotted in broadcast' is the wordplay.
'writer' becomes 'eye' (I can't justify this - if you can you should give a lot more credence to this answer).
'spotted' becomes 'saw' (I've seen this before).
'in broadcast' shows a homophone (sound like).
'saw' sounds like 'sore'.
'eye'+'sore'='EYESORE'
'the' acts as a link.
Can you help me to learn more?
(Other definitions for eyesore that I've seen before include "Thing that is ugly to look at" , "Blemish" , "Ugly prospect" , "pigsty" , "Blight" .)