It’s first class for us, travelling with Jack (4,4)
I believe the answer is:
four star
'it's first class' is the definition.
I know nothing about this answer so I can't tell whether it can be defined by this definition.
'for us travelling with jack' is the wordplay.
'travelling' is an anagram indicator.
'with' says to put letters next to each other.
'jack' becomes 'tar' (both are informal terms for sailor).
'for'+'us'='forus'
'forus' is an anagram of 'fours'.
'fours'+'tar'='FOUR-STAR'
Can you help me to learn more?
(Other definitions for four star that I've seen before include "Obsolescent type of petrol?" , "Like a general" .)