Ship with only half a yard to move? (4)
I believe the answer is:
argo
'ship' is the definition.
(ship in Greek myth)
'only half a yard to move?' is the wordplay.
'only half' means to take half the letters.
'a yard' becomes 'spar' (I've seen this in another clue).
'to move?' becomes 'go' (to go is to move).
'spar' with half the letters taken is 'ar'.
'ar'+'go'='ARGO'
'with' acts as a link.
(Other definitions for argo that I've seen before include "Jason's legendary ship" , "Ship used by Jason in his search for the Golden Fleece" , "Ancient ship" , "Name of ship sailed by Jason in search of the Golden Fleece" , "Old sailing vessel" .)