Be good at getting something for nothing? (3)

I believe the answer is:

beg

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'getting something for nothing?' is the definition.
I can't judge whether this definition defines the answer.

'be good' is the wordplay.
'good' becomes 'g' (abbreviation).
'be'+'g'='BEG'

'at' acts as a link.

Can you help me to learn more?

(Other definitions for beg that I've seen before include "Plead as for help" , "Plead in desperation" , "Plead or scrounge" , "Plead or ask for alms" , "Solicit charity" .)

I've seen this clue in the Evening Standard.

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