A guy will ring; say this when you pick up (5)

I believe the answer is:

hello

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'this when you pick up' is the definition.
The definition suggests a singular noun which matches the answer.

'a guy will ring' is the wordplay.
'a guy will' becomes 'hell' (contraction of 'he will').
'ring' becomes 'O' (letter resembling a ring).
'hell'+'o'='HELLO'

'say' acts as a link.

Can you help me to learn more?

(Other definitions for hello that I've seen before include "Musical with Satchmo and Streisand" , "Meeting greeting" , "Conversation starter" , "Conventional word of greeting" , "royals dominate its pages?" .)

I've seen this clue in The Irish Times.

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