Climbers limited by heaviness (5)
I believe the answer is:
vines
'climbers' is the definition.
(climbing plants)
'limited by heaviness' is the wordplay.
'limited by' indicates the answer is hidden within the clue (the clue contains or limits the answer).
'VINES' is hidden in the letters of 'heaviness'.
(Other definitions for vines that I've seen before include "Climbing or trailing plants" , "Grape plants" , "Grapes grow on them" , "Plants that climb and twine" , "Wine is ultimately the fruit of these" .)