Expelling yobs finally in day trip (7)
I believe the answer is:
ousting
'expelling' is the definition.
('oust' can be a synonym of 'expel')
'yobs finally in day trip' is the wordplay.
'finally' says to take the final letters.
'in' means one lot of letters goes inside another.
'day trip' becomes 'outing' (I've seen this before).
The final letter of 'yobs' is 's'.
's' going within 'outing' is 'OUSTING'.
(Other definitions for ousting that I've seen before include "ejecting" , "Turfing out" , "Driving out" , "Evicting" .)