Historic general or sailor boy (7)
I believe the answer is:
jackson
'historic general' is the definition.
Although both the answer and definition are singular nouns, I can't see how one could define the other.
'sailor boy' is the wordplay.
'sailor' becomes 'jack' (informal term for a sailor).
'boy' becomes 'son' (synonyms).
'jack'+'son'='JACKSON'
'or' is the link.
Can you help me to learn more?
(Other definitions for jackson that I've seen before include "American hero" , "American painter, 1912-56" , "See 13" , "Seventh US president Andrew - actress turned politician Glenda - singers Michael and Janet etc" , "Mississippi capital and 7th US president" .)