Vessel robot crashed in trench (9)
I believe the answer is:
'vessel' is the definition.
(motorboat is a kind of vessel)
'robot crashed in trench' is the wordplay.
'crashed' is an anagram indicator.
'in' means one lot of letters goes inside another.
'trench' becomes 'moat' (moat is a kind of trench).
'robot' with letters rearranged gives 'torbo'.
'torbo' going into 'moat' is 'MOTORBOAT'.
(Another definition for motorboat that I've seen is " powered vessel".)