Evenly plant fir on terrace (5)
I believe the answer is:
patio
'terrace' is the definition.
('patio' can be a synonym of 'terrace')
'evenly plant fir on' is the wordplay.
'evenly' means one should take alternating letters (even-numbered letters only).
'plant'+'fir'+'on'='plantfiron'
The alternating letters of 'plantfiron' are 'PATIO'.
(Other definitions for patio that I've seen before include "Paved area outside house" , "Paved outdoor area" , "Garden terrace" , "Where Barbie might be held" , "Inner courtyard" .)