measure

[vpesci]

unit of chain length in Britain equal to 75 feet

[mikewith]

bigmack had the most complete answer: "answer is shot (equivalent to 12 and half fathoms) see www.dictionary.com (I usially enter via www.onelook.com - great site for getting words when you only have a few letters by use of wildcards". So, the answer to this crossword question is: shot.