Canopy of trees disturbed by what, ultimately? (6)
I believe the answer is:
tester
'canopy' is the definition.
(I've seen this before)
'trees disturbed by what ultimately?' is the wordplay.
'disturbed' is an anagram indicator.
'by' means one lot of letters go next to another.
'ultimately?' says to take the final letters (I've seen 'ultimately' mean this).
The final letter of 'what' is 't'.
'trees' with letters rearranged gives 'ester'.
'ester' after 't' is 'TESTER'.
'of' is the link.
(Other definitions for tester that I've seen before include "One who tries out - canopy" , "Trial sample; bed canopy" , "covering at night" , "Canopy over mattress or an examiner" , "One sampling; four-poster bed canopy" .)