Expert came across, over for the time being (3,3)
I believe the answer is:
pro tem
'for the time being' is the definition.
('pro tem' can be a synonym of 'for the time being')
'expert came across over' is the wordplay.
'expert' becomes 'pro' (I've seen this before).
'came across' becomes 'met' ('meet' can be a synonym of 'come across').
'over' is a reversal indicator.
'met' in reverse letter order is 'tem'.
'pro'+'tem'='PRO TEM'
(Other definitions for pro tem that I've seen before include "For the present" , "For the time being (Latin abbreviation)" , "Informally, for the time being" , "'For the time being (3,3)'" , "For the time being, to the old Romans in short" .)