Chap calls aunt regularly (4)
I believe the answer is:
alan
'chap' is the definition.
(a chap named alan)
'calls aunt regularly' is the wordplay.
'regularly' indicates alternate letters (regularly take one letter, leave next etc.).
'calls'+'aunt'='callsaunt'
The alternate letters of 'callsaunt' are 'ALAN'.
(Other definitions for alan that I've seen before include "Boy's name" , "English name" , "Lana (anag.), man's name" , "-- Sugar, British entrepreneur" , "Boy" .)