State finds Boatman in picket (5)
I believe the answer is:
posit
'state' is the definition.
(I know that state can be written as posit)
'boatman in picket' is the wordplay.
'boatman' becomes 'I' (where the crossword setter is 'Boatman').
'in' is an insertion indicator.
'picket' becomes 'post' (I've seen this before).
'i' going into 'post' is 'POSIT'.
'finds' is the link.
(Other definitions for posit that I've seen before include "Suggest" , "given proposition" , "forward-looking statement" , "advance" , "Put forward; place" .)