Standing in lakeside greenhouse (6)
I believe the answer is:
degree
'standing' is the definition.
(thesaurus)
'in lakeside greenhouse' is the wordplay.
'in' says the answer is hidden in the clue.
'DEGREE' is hidden within 'lakeside greenhouse'.
(Other definitions for degree that I've seen before include "Unit of measurement of angle" , "Measure for angle and temperature" , "It's given to college graduates" , "an award at Edinburgh, maybe" , "small part" .)