Thora Hird's parts? (6)

I believe the answer is:

thirds

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'parts?' is the definition.

'thora hird's' is the wordplay.
'thora' becomes 't' (this might be a standard abbreviation of which I'm unaware).
't'+'hirds'='THIRDS'

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(Other definitions for thirds that I've seen before include "Three equal parts" , "Degrees" , "Musical intervals" , "sections" .)

I've seen this clue in the Evening Standard.

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