One who is new to environmental instrument (9)

I believe the answer is:

greenhorn

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'one who is new' is the definition.
The answer is a person as well as being a singular noun. This is suggested by the definition.

'environmental instrument' is the wordplay.
'environmental' becomes 'green'.
'instrument' becomes 'horn' (horn is a kind of instrument).
'green'+'horn'='GREENHORN'

'to' acts as a link.

Can you help me to learn more?

(Other definitions for greenhorn that I've seen before include "One learning" , "One's not experienced" , "colt" , "An inexperienced person of emerald hue?" , "Novice" .)

I've seen this clue in The Daily Express.

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