Topical variation? That's mine! (7)

I believe the answer is:

coalpit

'mine' is the definition.
(coalpit is a kind of mine)

'topical variation?' is the wordplay.
'variation?' indicates an anagram (I've seen 'variation' mean this).
'topical' is an anagram of 'COALPIT'.

'that's' is the link.

(Another definition for coalpit that I've seen is " mine".)

I've seen this clue in The Independent.

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