Inkling that there's an informer in your midst? (8,9)

'inkling that there's' is the definition.
'sneaking suspicion' can be an answer for 'inkling' (thesaurus). I am not sure about the remainder of the definition.

'informer in your midst?' is the wordplay.
I cannot really understand how this works, but
'informer' could be 'sneak' (sneak is a kind of informer) and 'sneak' is located in the answer.
'in' is found in the answer.
This explanation may well be incorrect...

'an' acts as a link.

Can you help me to learn more?