Reserve surprisingly nice tree, cheap initially (9)
I believe the answer is:
reticence
'reserve' is the definition.
('reticence' can be a synonym of 'reserve')
'surprisingly nice tree cheap initially' is the wordplay.
'surprisingly' is an anagram indicator.
'initially' says to take the initial letters.
The initial letter of 'cheap' is 'c'.
'nice'+'tree'+'c'='nicetreec'
'nicetreec' with letters rearranged gives 'RETICENCE'.
(Other definitions for reticence that I've seen before include "Tendency to hold back" , "Tendency to be reserved in communication" , "modesty" , "'Reserve, taciturnity (9)'" , "Unwillingness to talk" .)