Rapid drop in folio, bank finished with completely (4,4)
I believe the answer is:
free fall
'rapid drop' is the definition.
'folio bank finished with completely' is the wordplay.
'folio' becomes 'f' (abbreviation listed in Chambers).
'bank' becomes 'reef' (I've seen this before).
'finished with' says to put letters next to each other.
'completely' becomes 'all' ('all' can be a synonym of 'completely').
'f'+'reef'+'all'='FREE FALL'
'in' acts as a link.
(Other definitions for free fall that I've seen before include "Uncontrolled plunge" , "skydiving practice?" , "Rapid descent (before parachute opens, for example)" , "Drop with parachute unopened" , "Downward movement under the force of gravity" .)