Old Yankee traps park-keeper in hothouse (8)
I believe the answer is:
orangery
'hothouse' is the definition.
(thesaurus)
'old yankee traps park-keeper' is the wordplay.
'old' becomes 'o' (common abbreviation eg in OE for Old English).
'yankee' becomes 'y' (phonetic alphabet: alpha, bravo, charlie etc.).
'traps' means one lot of letters goes inside another.
'park keeper' becomes 'ranger' (I've seen this before).
'o'+'y'='oy'
'oy' enclosing 'ranger' is 'ORANGERY'.
'in' is the link.
(Other definitions for orangery that I've seen before include "Plant-house" , "Conservatory for growing citrus plants" , "cultivated area" , "fruit source" , "Building for citrus growing" .)