See CID tip off killer in field? (9)

I believe the answer is:

pesticide

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'killer in field?' is the definition.
'pesticide' can be an answer for 'killer' (thesaurus). I am not certain of the 'in field?' bit.

'see cid tip off' is the wordplay.
'off' is an anagram indicator.
'see'+'cid'+'tip'='seecidtip'
'seecidtip' with letters rearranged gives 'PESTICIDE'.

Can you help me to learn more?

(Other definitions for pesticide that I've seen before include "It kills harmful creatures" , "Insect killer" , "From poison" , "What eliminates bugs" .)

I've seen this clue in The Times.

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