Power-driven craft uncle has designed (8)
I believe the answer is:
launches
'power-driven craft' is the definition.
I can't judge whether this definition defines the answer.
'uncle has designed' is the wordplay.
'designed' indicates an anagram (designed with the letters).
'uncle'+'has'='unclehas'
'unclehas' with letters rearranged gives 'LAUNCHES'.
Can you help me to learn more?
(Other definitions for launches that I've seen before include "Motorboats" , "Sets afloat - motor boats" , "Sets a boat afloat" , "Sends on its course, like a ship" , "Sets in motion,a ship say" .)