Building set in holy place? Forget it! (7)
I believe the answer is:
meccano
'building set in holy' is the definition.
The definition suggests a singular noun which matches the answer.
'place? forget it' is the wordplay.
'place?' becomes 'mecca' (I have seen 'Place of pilgrimage' mean 'mecca' so perhaps 'place' could also mean 'mecca').
'forget it' becomes 'no' (I can't explain this - if you can you should give a lot more credence to this answer).
'mecca'+'no'='MECCANO'
Can you help me to learn more?
(Other definitions for meccano that I've seen before include "Material to construct" , "It's for kids' building" , "Plaything" , "constructive materials" , "Children's nuts and bolts kit" .)