Tree an Isle of Man company cut? (7,3)

I believe the answer is:

douglas fir

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'tree an isle' is the definition.
'douglas fir' can be an answer for 'tree' (I've seen this before). I am not certain of the 'an isle' bit.

'man company cut?' is the wordplay.
'man' becomes 'douglas' ().
'company' becomes 'firm' (firm can mean a company or business).
'cut?' means to remove the last letter (I've seen 'cutting' mean this).
'firm' with its last letter taken off is 'fir'.
'douglas'+'fir'='DOUGLAS FIR'

'of' is the link.

Can you help me to learn more?

(Another definition for douglas fir that I've seen is " tree".)

I've seen this clue in The Telegraph.

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