Had ghosts appearing regularly (3)
I believe the answer is:
got
'had' is the definition.
('get' can be a synonym of 'have')
'ghosts appearing regularly' is the wordplay.
'appearing regularly' means one should take alternating letters.
The alternate letters of 'ghosts' are 'GOT'.
(Other definitions for got that I've seen before include "Received; understood" , "Caught" , "Obtained" , "came by" , "Acquired" .)