Upset about unoccupied lab being used by inferior amateur (7)

I believe the answer is:

dabbler

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'amateur' is the definition.
(dabbler is a kind of amateur)

'upset about unoccupied lab being used by inferior' is the wordplay.
'upset' is a reversal indicator.
'about' becomes 're' ('re' means regarding or about).
'unoccupied' suggests removing the centre (remove the inside letters which occupy the word).
'being used by inferior' becomes 'bad' (I am not sure about this - if you are sure you should give a lot more credence to this answer).
'lab' with its centre removed is 'lb'.
're'+'lb'+'bad'='relbbad'
'relbbad' back-to-front is 'DABBLER'.

Can you help me to learn more?

(Other definitions for dabbler that I've seen before include "Dilettante" , "amateur" , "Someone with passing interest" .)

I've seen this clue in The Irish Times.

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