Doddery old aunt grown tedious (4-5-3)
I believe the answer is:
long-drawn-out
'tedious' is the definition.
(I've seen this before)
'doddery old aunt grown' is the wordplay.
'doddery' indicates anagramming the letters.
'old'+'aunt'+'grown'='oldauntgrown'
'oldauntgrown' with letters rearranged gives 'LONG-DRAWN-OUT'.
(Other definitions for long-drawn-out that I've seen before include "Unduly protracted" , "Unduly extended" .)