An Arab boat? Very much so! (3,3)
I believe the answer is:
and how
'so' is the definition.
Both the definition and answer are adverbs. Maybe there's a link between them I don't understand?
'an arab boat? very much' is the wordplay.
'arab boat?' becomes 'dhow' (I've seen this in another clue).
'very' becomes 'v' (common abbreviation).
'much' means to remove the last letter (much but not all of the word).
'an'+'dhow'+'v'='andhowv'
'andhowv' with its final letter removed is 'AND HOW!'.
Can you help me to learn more?
(Another definition for and how that I've seen is " Certainly".)