Loving a room designed by American (7)
I believe the answer is:
amorous
'loving' is the definition.
(similar in meaning)
'a room designed by american' is the wordplay.
'designed' indicates an anagram (designed with the letters).
'by' means one lot of letters go next to another.
'american' becomes 'us' (abbreviation for United States).
'room' with letters rearranged gives 'moro'.
'a'+'moro'+'us'='AMOROUS'
(Other definitions for amorous that I've seen before include "Impassioned and loving" , "Lustful" , "Possessed of loving or romantic feeling" , "Inclined towards displaying love" , "Expressing love" .)