Climbing frame (6)
'climbing frame?' is the definition.
(I've seen this before)
This is all the clue.
(Other definitions for ladder that I've seen before include "Run in stockings" , "Row of unravelled stitches" , "Unravel (as stocking)" , "A fire-fighter may use one" , "Climbing frame; damage tights" .)
(Other definitions for trellis that I've seen before include "Latticework for climbing plants" , "Latticed frame" , "Garden climbing frame" , "Plant-training lattice" , "where climbers may be trained" .)