Short nail (4)
'short nail' is the definition.
(I've seen this before)
This is all the clue.
(Other definitions for tack that I've seen before include "policy" , "Nail - direction (eg of boat)" , "Type of nail" , "Change course < material" , "Small nail; sail (boat) against the wind" .)
'short nail' is the definition.
(I've seen this in another clue)
This is the entire clue.
(Other definitions for brad that I've seen before include "Type of nail" , "Small-headed nail" , "Small tapering nail" , "One to get hammered" , "One may secure" .)