I worked out what the answer is but had to check it because I had never heard of the word.
I do the Metro cryptic crossword most days and occasionally come across that sort of clue. I don't count it as 'cheating' to check a word once I have deduced what it must be and I usually remember the word the next time that it comes round. If you do crosswords often enough you start to notice that clues get repeated. I had never heard of 'besom' until last year (a broom made of twigs tied round a stick, or witch's broomstick) but I have seen it at least another 2 or 3 times since then. Similarly, 'samovar' (Russian tea urn) etc.