Fiona, Vera, Geraldine hid, typically (2,7)
I believe the answer is:
on average
'typically' is the definition.
(I've seen this before)
'fiona vera geraldine hid' is the wordplay.
'hid' says the answer is hidden in the clue (I've seen 'hides' mean this).
'ON AVERAGE' is hidden in the letters of 'fiona vera geraldine'.
(Other definitions for on average that I've seen before include "Generally" , "typically speaking" , "Usually" .)