I tested them at work to check the flow (4,3,4)

I believe the answer is:

stem the tide

'check the flow' is the definition.

'i tested them at work' is the wordplay.
'at work' indicates anagramming the letters.
'i'+'tested'+'them'='itestedthem'
'itestedthem' anagrammed gives 'STEM THE TIDE'.

'to' is the link.

I've seen this clue in The Guardian.

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