Boatman has appeal but not much (1,3)
I believe the answer is:
a bit
'not much' is the definition.
(a bit can mean a small amount)
'boatman has appeal' is the wordplay.
'boatman' becomes 'ab' (abbreviation for able seaman).
'has' says to put letters next to each other.
'appeal' becomes 'it' ('it' can mean something attractive or appealing).
'ab'+'it'='A BIT'
'but' is the link.
(Other definitions for a bit that I've seen before include "Rather" , "to some extent" , "Somewhat" , "fairly?" , "Slightly" .)