Extremities of planet full of spirit (7)

I believe the answer is:

margins

'extremities' is the definition.
(margins can mean extremities or limits)

'planet full of spirit' is the wordplay.
'planet' becomes 'mars' (Mars is a planet).
'full of' indicates putting letters inside.
'spirit' becomes 'gin' (alcoholic spirit).
'mars' placed around 'gin' is 'MARGINS'.

'of' acts as a link.

(Another definition for margins that I've seen is " Profits".)

I've seen this clue in The Guardian.

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