Give people a hand with cases for departure and arrival (4)
I believe the answer is:
deal
'give people a hand' is the definition.
(to deal a 'hand' in card games)
'cases for departure and arrival' is the wordplay.
'cases for' suggests removing the centre (I've seen 'case for' mean this (the letters which encase the others are used)).
'and' is a charade indicator (letters next to each other).
'arrival' becomes 'al' (I am not sure about this - if you are sure you should believe this answer much more).
'departure' with its centre removed is 'de'.
'de'+'al'='DEAL'
'with' acts as a link.
Can you help me to learn more?
(Other definitions for deal that I've seen before include "understanding" , "Plank of softwood timber" , "Kent town" , "Agreement; soft wood" , "Trade; pine wood" .)