Thora Hird's shortened part (5)

I believe the answer is:

third

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'part' is the definition.
(fraction)

'thora hird's shortened' is the wordplay.
'thora' becomes 't' (this might be a standard abbreviation I've not previously seen).
'shortened' means to remove the last letter.
'hirds' with its final letter taken away is 'hird'.
't'+'hird'='THIRD'

Can you help me to learn more?

(Other definitions for third that I've seen before include "Eroica, Beethoven's - symphony" , "Musical interval" , "One of three equal parts" , "33 per cent" , "Ruthless interrogation" .)

I've seen this clue in The Irish Independent.

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