Don’t argue – change gear, sweetheart! (5)

I believe the answer is:

agree

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

'don't argue' is the definition.
I can't judge whether this definition defines the answer.

'change gear sweetheart' is the wordplay.
'change' is an anagram indicator.
'sweetheart' becomes 'e' (the heart/centre of 'sweet'**).
'gear' anagrammed gives 'agre'.
'agre'+'e'='AGREE'

Can you help me to learn more?

(Other definitions for agree that I've seen before include "Arrive at a settlement" , "Concur, acquiesce" , "Square" , "Concur, coincide" , "Accord, match" .)

I've seen this clue in the Evening Standard.

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