Screws not for fixing high platform (5,4)
I believe the answer is:
crows nest
'platform' is the definition.
(crow's nest is a kind of platform)
'screws not for fixing high' is the wordplay.
'screws not' can be anagrammed to 'CROW'S-NEST'.
However, I am not clear how this is indicated.
Can you help me to learn more?
(Other definitions for crows nest that I've seen before include "high naval post" , "lookout post" , "elevated lookout platform" .)