Generous, holding back –then old will board vehicle that’s almost full (7)
I believe the answer is:
gibbous
'almost full' is the definition.
I can't judge whether this defines the answer.
'generous holding back then old will board vehicle' is the wordplay.
'generous holding back then' becomes 'gib' (I can't justify this - if you can you should give a lot more credence to this answer).
'old' becomes 'o' (abbreviation).
'will board' indicates putting letters inside.
'vehicle' becomes 'bus' (public transport vehicle).
'o' inserted within 'bus' is 'bous'.
'gib'+'bous'='GIBBOUS'
'that's' is the link.
Can you help me to learn more?
(Other definitions for gibbous that I've seen before include "(Of moon) more than half visible" , "(Of moon) mostly, but not wholly, illuminated" , "(Moon) short of full" .)