Screws not tight where sailor perches (5,4)
I believe the answer is:
crows nest
'where sailor perches' is the definition.
Although both the answer and definition are singular nouns, I don't see how they can define each other.
'screws not tight' is the wordplay.
'tight' indicates an anagram (tight can mean drunk).
'screws'+'not'='screwsnot'
'screwsnot' with letters rearranged gives 'CROWS-NEST'.
Can you help me to learn more?
(Other definitions for crows nest that I've seen before include "high naval post" , "elevated lookout platform" , "lookout post" .)