I see one fish (3)

I believe the answer is:
ahi
'fish' is the definition.
I know nothing about this answer so I can't tell whether this works.
'i see one' is the wordplay.
'i see' becomes 'ah' ('ah' can be used to express understanding).
'one' becomes 'i' (Roman numeral).
'ah'+'i'='AHI'
Can you help me to learn more?
(Another definition for ahi that I've seen is " tuna".)
I've seen this clue in The Independent.
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