Restriction coming over time — it is an eye problem (9)

I believe the answer is:

retinitis

'an eye problem' is the definition.
(inflammation of the retina)

'restriction coming over time it is' is the wordplay.
'restriction' becomes 'rein' (reins control or restrict an animal).
'coming over' is an insertion indicator (some letters go around or come over others).
'time' becomes 't' (abbreviation).
'rein' placed around 't' is 'retin'.
'retin'+'it'+'is'='RETINITIS'

I've seen this clue in The Guardian.

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