A French girl briefly stood up to strip on boat (5)
I believe the answer is:
unrig
'strip on boat' is the definition.
'a french girl briefly stood up' is the wordplay.
'a french' becomes 'un' ('a' in French).
'briefly' means to remove the last letter.
'stood up' is a reversal indicator (in a down clue, letters go up).
'girl' with its final letter taken off is 'gir'.
'gir' in reverse letter order is 'rig'.
'un'+'rig'='UNRIG'
'to' is the link.
(Other definitions for unrig that I've seen before include "Take down sails" , "In rug (anag.)" , "Take tackle out" , "(Of a boat) strip of its mast, stays etc" , "Dismantle" .)