Ship yet to launch, boat ultimately motionless (5)
I believe the answer is:
inert
'motionless' is the definition.
(inertia is a lack of movement)
'ship yet to launch boat ultimately' is the wordplay.
'ship' becomes 'liner' (liner is a kind of ship).
'yet to launch' means to remove the first letter (the letter which launches the word is not there).
'ultimately' suggests the final letters.
The last letter of 'boat' is 't'.
'liner' with its first letter taken away is 'iner'.
'iner'+'t'='INERT'
(Other definitions for inert that I've seen before include "Disinclined to act" , "Unmoving" , "Unreactive; still" , "like neon" , "Lifeless, sluggish" .)