In different camps around river that’s very small (10)

I believe the answer is:

fractional

'very small' is the definition.
(as in a fractional increase)

'in different camps around river' is the wordplay.
'in different camps' becomes 'factional' (a faction is a camp or wing).
'around' indicates putting letters inside.
'river' becomes 'r' (abbreviation for river).
'factional' enclosing 'r' is 'FRACTIONAL'.

'that's' acts as a link.

(Another definition for fractional that I've seen is " Very little".)

I've seen this clue in The Times.

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