Phone feature increases values (9)
I believe the answer is:
appraises
'values' is the definition.
('appraise' can be a synonym of 'value')
'phone feature increases' is the wordplay.
'phone feature' becomes 'app' (I've seen this in another clue).
'increases' becomes 'raises' (raising is a kind of increasing).
'app'+'raises'='APPRAISES'
(Other definitions for appraises that I've seen before include "Rates" , "Assesses" .)