Some words for actor are mostly a former script (6,1)

I believe the answer is:

linear a

'former script' is the definition.
(ancient writing)

'some words for actor are mostly a' is the wordplay.
'some words for actor' becomes 'line' (a line of dialogue).
'mostly' means to remove the last letter.
'are' with its final letter taken off is 'ar'.
'line'+'ar'+'a'='LINEAR A'

(Another definition for linear a that I've seen is " script yet to be read".)

I've seen this clue in The Times.

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