Fox coming from marshy land with endless boldness (6)
I believe the answer is:
boggle
'fox' is the definition.
(both can mean to confuse)
'marshy land with endless boldness' is the wordplay.
'marshy land' becomes 'bog' (a bog is a wet or marshy area).
'with' says to put letters next to each other.
'endless' means to remove the last letter.
'boldness' becomes 'glee' (bold or unrestrained happiness).
'glee' with its last letter removed is 'gle'.
'bog'+'gle'='BOGGLE'
'coming from' is the link.
(Other definitions for boggle that I've seen before include "Baffle or fluster" , "Fluster and flabbergast" , "Be startled or baffled (colloq.)" , "Confuse and fluster" , "Overcome with amazement" .)