Reassembled fleet with haste set out at night (5,5)
I believe the answer is:
false teeth
'set out at night' is the definition.
(I've seen this before)
'reassembled fleet with haste' is the wordplay.
'reassembled' indicates anagramming the letters.
'with' means one lot of letters go next to another.
'fleet' put after 'haste' is 'hastefleet'.
'hastefleet' anagrammed gives 'FALSE TEETH'.
(Other definitions for false teeth that I've seen before include "Plates" , "set out at night" , "Denture's components" , "Choppers that may be taken out" , "New gnashers!" .)