Too old? True, about fifty (6)

I believe the answer is:

overly

'too' is the definition.
(I know that too can be written as overly)

'old? true about fifty' is the wordplay.
'old?' becomes 'o' (common abbreviation eg in OE for Old English).
'true' becomes 'very' (I've seen this in other clues).
'about' is an insertion indicator.
'fifty' becomes 'l' (Roman numeral).
'very' going around 'l' is 'verly'.
'o'+'verly'='OVERLY'

(Another definition for overly that I've seen is " Excessively".)

I've seen this clue in The Times.

Want a hint initially instead of a full solution? Install my app