Imperial unit might put shore manoeuvre first (10)
I believe the answer is:
horsepower
'imperial unit' is the definition.
'horsepower' can be an answer for 'unit' (horsepower is a kind of unit). I'm unsure of the 'imperial' bit.
'might put shore manoeuvre first' is the wordplay.
I cannot quite understand how this works, but
'might' could be 'power' (being mighty) and 'power' is found in the answer.
an anagram of 'shore' is 'horse' which is located in the answer.
No letters remain.
This explanation may well be incorrect...
Can you help me to learn more?
(Other definitions for horsepower that I've seen before include "Measure of force" , "Unit equal to about 750 watts" , "Rep who rose (anag) - equivalent of 745.7 watts" , "Unit of power" , "measure of strength" .)