The two of us plot to kidnap bachelor with a skinny joiner (6)
I believe the answer is:
webbed
'with a skinny joiner' is the definition.
(as in webbed-feet, with skin joining digits)
'the two of us plot to kidnap bachelor' is the wordplay.
'the two of us' becomes 'we' (you and I).
'plot' becomes 'bed' (a plot of land).
'to kidnap' indicates putting letters inside (inserted letters are kidnapped or taken).
'bachelor' becomes 'B' (abbreviation e.g. BA=Bachelor of Arts).
'bed' placed around 'b' is 'bbed'.
'we'+'bbed'='WEBBED'
(Other definitions for webbed that I've seen before include "Describing feet where digits are linked by membrane" , "Condition of duck's feet" , "Having the toes connected by a membrane, as a waterbird" , "Nature of duck's feet" , "Like duck's feet" .)