Install gong, terribly durable (4-7)

I believe the answer is:

long-lasting

'durable' is the definition.
(I know that durable can be written as long-lasting)

'install gong terribly' is the wordplay.
'terribly' indicates anagramming the letters.
'install'+'gong'='installgong'
'installgong' with letters rearranged gives 'LONG-LASTING'.

(Another definition for long-lasting that I've seen is " Durable".)

I've seen this clue in The Mirror.

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