A side’s competitive keenness? (4)

I believe the answer is:

edge

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This might be a double definition.

'a side's' is the first definition.
(edge is a kind of side)

'competitive keenness?' is the second definition.
'edge' can be an answer for 'keenness?' (thesaurus). I am unsure of the 'competitive' bit.

Can you help me to learn more?

(Other definitions for edge that I've seen before include "incisiveness" , "Demarcation" , "Sharp side of a blade" , "Lip; advantage" , "Move slowly" .)

I've seen this clue in the Evening Standard.

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