Observe to be wordy (7)
I believe the answer is:
verbose
'wordy' is the definition.
(I know that wordy can be written as verbose)
'observe to be' is the wordplay.
'to be' indicates anagramming the letters.
'observe' anagrammed gives 'VERBOSE'.
(Other definitions for verbose that I've seen before include "'Long-winded, wordy (7)'" , "Loquacious" , "Using too many words, too talkative" , "With an excess of words" , "Wordy, prolix" .)