Made certain it had been securely fastened (8)
I believe the answer is:
clinched
'fastened' is the definition.
(clinching is a kind of fastening)
'made certain it had been securely' is the wordplay.
I cannot really see how this works, but
'it' could be 'e' ('e' can mean 'electronic' which is similar to 'IT') and 'e' is found in the answer.
'had' could be 'd' (I've seen this in other clues) and 'd' is present in the answer.
The remaining letters 'clinch' is a valid word which might be clued in a way I don't understand.
This may be the basis of clue (or it may be nonsense).
Can you help me to learn more?
(Other definitions for clinched that I've seen before include "Secured" , "fastened securely" , "Embraced tightly" .)