Talent hero developed to be very attentive (2,3,5)

I believe the answer is:

on the alert

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

'very attentive' is the definition.
'on the alert' can be an answer for 'attentive' (thesaurus). I'm unsure of the 'very' bit.

'talent hero developed' is the wordplay.
'developed' is an anagram indicator.
'talent'+'hero'='talenthero'
'talenthero' anagrammed gives 'ON THE ALERT'.

'to be' acts as a link.

Can you help me to learn more?

(Other definitions for on the alert that I've seen before include "vigilant" , "Looking out" .)

I've seen this clue in The Independent.

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