Jack gets Rosalie no end upset! (6)
I believe the answer is:
Here is my best explanation:
'jack' is the definition.
(I've seen this before)
'rosalie no end upset' is the subsidiary indication.
'no end' means to remove the last letter.
'upset' indicates anagramming the letters.
'rosalie' with its last letter taken off is 'rosali'.
'rosali' is an anagram of 'sailor'.
'gets' is the link.
(Other definitions for sailor that I've seen before include "Sinbad, maybe", "Matelot", "Seafarer", "Seaman", "Mariner", "Old salt", "Sinbad, for example", "Ship's crew member", "Jack" and "Crew member".)