Relative, first of all, getting rather ancient now (4)

I believe the answer is:

gran

'relative' is the definition.
(I know that gran is a type of mothers)

'first of all getting rather ancient now' is the wordplay.
'first of all' suggests taking the first letters.
The first letters of 'getting rather ancient now' is 'GRAN'.

(Other definitions for gran that I've seen before include "Rang (anag.)" , "Older relative" , "Senior family member" , "Mum's mum" , "nan" .)

I've seen this clue in The Telegraph.

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