Policeman’s lying about keeping agreement in an unnerving way (15)

I believe the answer is:

disconcertingly

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'an unnerving way' is the definition.
I can't tell whether this defines the answer.

'policeman's lying about keeping agreement' is the wordplay.
'policeman's' becomes 'di's' (detective inspector).
'about' is an anagram indicator.
'keeping' indicates putting letters inside (some letters kept inside).
'agreement' becomes 'concert' (I am not sure about this - if you are sure you should give a lot more credence to this answer).
'lying' is an anagram of 'ingly'.
'ingly' placed around 'concert' is 'concertingly'.
'dis'+'concertingly'='DISCONCERTINGLY'

'in' is the link.

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I've seen this clue in The Times.

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