Keeps a close eye on, though there’s no longer any resistance (6,4)

'there's no longer any resistance' is the definition.
I know nothing about this answer so I cannot tell whether it can be defined by this definition.

'keeps a close eye on' is the wordplay.
I cannot quite see how this works, but
'a' could be 'an' and 'an' is present in the answer.
'on' could be 'over' (I've seen this in other clues) and 'over' is located in the answer.
The remaining letters 'stds' is a valid word which might be clued in a way I don't understand.
This explanation may well be incorrect...

'though' is the link.

Can you help me to learn more?