Crossword Genius

Act as a paid informer (5)

Ross

I believe the answer is:

teach

I'm a little stuck... Click here to teach me more about this clue!

'act' is the definition.
Although both the answer and definition are verbs in their base form, I cannot understand how they can define each other.

'a paid informer' is the wordplay.
I cannot quite understand how this works, but
'a' is found in the answer.
The remaining letters 'tech' is a valid word which might be clued in a way I don't understand.
This may be the basis of the clue (or it may be nonsense).

'as' acts as a link.

Can you help me to learn more?

(Other definitions for teach that I've seen before include "Provide learning to" , "Blackbeard" , "Impart skills or 3 down" , "Act as director" , "Coach" .)

I've seen this clue in The Globe and Mail.
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