Connell regularly meets Peggy, at last alone (4)
I believe the answer is:
only
'alone' is the definition.
(synonyms)
'connell regularly meets peggy at last' is the wordplay.
'regularly' indicates alternate letters (regularly take one letter, leave next etc.).
'meets' is a charade indicator (letters next to each other).
'at last' suggests the final letters.
The last letter of 'peggy' is 'y'.
The alternating letters of 'connell' are 'onl'.
'onl'+'y'='ONLY'
(Other definitions for only that I've seen before include "Solely, lone" , "See 6" , "Alone; solitary" , "Mere" , "Simply" .)