Bitterness associated with age-old craft (7)
I believe the answer is:
galleon
'old craft' is the definition.
'galleon' can be an answer for 'craft' (type of ship). I'm not certain of the 'old' bit.
'bitterness associated with age' is the wordplay.
'bitterness' becomes 'gall' (synonyms).
'associated with' is a charade indicator (letters next to each other).
'age' becomes 'eon' (eon is a kind of age).
'gall'+'eon'='GALLEON'
Can you help me to learn more?
(Other definitions for galleon that I've seen before include "Large old sailing vessel" , "Large Spanish sailing ship of yore" , "Trader" , "Large old square-rigged sailing ship" , "All gone (anag.)" .)