Notice a dog inside and tie it up (6)
I believe the answer is:
secure
'tie it up' is the definition.
I can't tell whether this definition defines the answer.
'notice a dog inside' is the wordplay.
'notice' becomes 'see' (notice can mean to spot or see).
'a dog' becomes 'cur' (both can mean a despicable person).
'inside' is an insertion indicator.
'see' enclosing 'cur' is 'SECURE'.
'and' is the link.
Can you help me to learn more?
(Other definitions for secure that I've seen before include "Reliable; firmly fixed" , "Fixed or fastened so as not to give way" , "'Safe, confident (6)'" , "Safe against attack or well fastened" , "Safe; fixed" .)