Garden limb on mast's beam (7)
I believe the answer is:
yardarm
'mast's beam' is the definition.
'yardarm' can be an answer for 'beam' (type of wooden beam on a ship). I'm not sure about the 'mast's' bit.
'garden limb on' is the wordplay.
'garden' becomes 'yard' (I have seen 'American garden' mean 'yard' so perhaps 'garden' could also mean 'yard').
'limb' becomes 'arm' (arm is a kind of limb).
'on' is a charade indicator (letters next to each other).
'yard'+'arm'='YARDARM'
Can you help me to learn more?
(Other definitions for yardarm that I've seen before include "The sun is over the -- means it's time for a drink" , "Beam on board" , "End of stout pole" , "End of spar on ship's mast" , "Tapering end of beam hung on mast" .)