Average. All about tricky age relating to auxiliary aspects of the law (9)
I believe the answer is:
paralegal
'relating to auxiliary aspects of the law' is the definition.
I can't judge whether this definition defines the answer.
'average all about tricky age' is the wordplay.
'average' becomes 'par' (I've seen this before).
'about' means one lot of letters goes inside another.
'tricky' indicates an anagram.
'age' is an anagram of 'ega'.
'all' placed around 'ega' is 'alegal'.
'par'+'alegal'='PARALEGAL'
Can you help me to learn more?
(Other definitions for paralegal that I've seen before include "Assistant in brief, say" , "brief support?" , "one serving person at the bar" , "one helps with soliciting?" .)