Skill in visualising successful movement of men on board? (15)
I believe the answer is:
draughtsmanship
'skill in visualising' is the definition.
(draughtsmanship is drawing or sketching)
'successful movement of men on board?' is the wordplay.
I cannot quite understand how this works, but
'men on board?' could be 'draughts' (I've seen this before) and 'draughts' is present in the answer.
This may be the basis of clue (or it may be nonsense).
(Other definitions for draughtsmanship that I've seen before include "ability to draw" , "skill (on paper)" , "drawing" , "Artistic skill" .)