Narrowing I have on pipe overhead (9)

I believe the answer is:

reductive

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'narrowing' is the definition.
Both the definition and answer are adjectives. Maybe there's an association between them I don't understand?

'i have on pipe overhead' is the wordplay.
'i have' becomes 'I've' (contraction of 'I have').
'on' becomes 're' (regarding).
'pipe' becomes 'duct' (I've seen this in another clue).
'overhead' means one lot of letters go next to another (in a down clue, some letters go over others).
're'+'duct'='reduct'
'ive' after 'reduct' is 'REDUCTIVE'.

Can you help me to learn more?

I've seen this clue in The Independent.

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