Upper-class art initial adjusting makes functional (11)
I believe the answer is:
utilitarian
'functional' is the definition.
('utilitarian' can be similar in meaning to 'functional')
'upper-class art initial adjusting' is the wordplay.
'upper-class' becomes 'u' ('u' can be similar in meaning to 'upper-class').
'adjusting' indicates an anagram.
'art'+'initial'='artinitial'
'artinitial' anagrammed gives 'tilitarian'.
'u'+'tilitarian'='UTILITARIAN'
'makes' acts as a link.
(Other definitions for utilitarian that I've seen before include "Philosopher" , "Practical rather than attractive" .)