Former heads of our legal department (3)

I believe the answer is:

old

'former' is the definition.
(thesaurus)

'heads of our legal department' is the wordplay.
'heads of' says to take the initial letters.
The initial letters of 'our legal department' is 'OLD'.

(Other definitions for old that I've seen before include "Senescent" , "Venerable" , "Former; aged" , "SECOND PART OF 14" , "Obsolete" .)

I've seen this clue in The Times.

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