Caught in no-go area, left by night (9)
I believe the answer is:
nocturnal
'by night' is the definition.
(I've seen this before)
'caught in no-go area left' is the wordplay.
'caught' becomes 'ct'.
'in' means one lot of letters goes inside another.
'go area left' becomes 'urnal' (I can't justify this - if you can you should give a lot more credence to this answer).
'no'+'urnal'='nournal'
'ct' inserted inside 'nournal' is 'NOCTURNAL'.
Can you help me to learn more?
(Other definitions for nocturnal that I've seen before include "Like owls and badgers" , "Like bats" , "Active at night" , "Appertaining to the night" , "going abroad furtively?" .)