Old-fashioned chair in current use (7)
I believe the answer is:
archaic
'old' is the definition.
(similar in meaning)
'fashioned chair in current use' is the wordplay.
'fashioned' is an anagram indicator.
'in' means one lot of letters goes inside another.
'current use' becomes 'ac' (I can't explain this - if you can you should believe this answer much more).
'chair' is an anagram of 'rchai'.
'rchai' inserted inside 'ac' is 'ARCHAIC'.
Can you help me to learn more?
(Other definitions for archaic that I've seen before include "Belonging to former times, perhaps word usage" , "Antiquated" , "From the past" , "A long way out of date" , "Antiquarian" .)