Round with park officer at end of day in greenhouse (8)
I believe the answer is:
orangery
'greenhouse' is the definition.
(thesaurus)
'round with park officer at end of day' is the wordplay.
'round' becomes 'o' (round can mean a round object).
'with' means one lot of letters go next to another.
'park officer' becomes 'ranger' (I've seen this before).
'at end of' suggests the final letters.
The final letter of 'day' is 'y'.
'o'+'ranger'+'y'='ORANGERY'
'in' is the link.
(Other definitions for orangery that I've seen before include "Greenhouse full of citrus trees" , "Greenhouse for citrus plants" , "Building in which citrus fruits are grown" , "tree house?" , "Plant-house" .)