Old storyteller regularly made use of PA (5)
I believe the answer is:
aesop
'old storyteller' is the definition.
'aesop' can be an answer for 'storyteller' (Aesop is an example). I'm unsure of the 'old' bit.
'regularly made use of pa' is the wordplay.
'regularly' indicates alternate letters (regularly take one letter, leave next etc.).
'made'+'use'+'of'+'pa'='madeuseofpa'
The alternate letters of 'madeuseofpa' are 'AESOP'.
Can you help me to learn more?
(Other definitions for aesop that I've seen before include "Great Greek teller of animal fables" , "he wrote in Greek" , "Author of many fables" , "Fable-teller" , "So ape the writer of fables" .)