Had gone by boat and the son was sick (6)
I believe the answer is:
sailed
'had gone by boat' is the definition.
Although both the answer and definition are past participle verbs, I cannot understand how they can define each other.
'the son was sick' is the wordplay.
'the son' becomes 's' (genealogical abbreviation for son).
'was sick' becomes 'ailed' (I've seen this in another clue).
's'+'ailed'='SAILED'
'and' is the link.
Can you help me to learn more?
(Other definitions for sailed that I've seen before include "Travelled by wind over water" , "Travelled by boat" .)