Old character I set up as representation of important person (5)
I believe the answer is:
imago
'representation of important person' is the definition.
'imago' can be an answer for 'representation' (I have seen 'ideal representation' mean 'imago' so perhaps 'representation' could also mean 'imago'). I am not certain of the 'of important person' bit.
'old character i set up' is the wordplay.
'old character' becomes 'ogam' (I've seen this before).
'set up' is a reversal indicator (in a down clue, letters go up).
'ogam'+'i'='ogami'
'ogami' backwards is 'IMAGO'.
'as' is the link.
Can you help me to learn more?
(Other definitions for imago that I've seen before include "latest development in cricket?" , "Insect at end of life" , "Mature insect after metamorphosis" , "idealised figure" , "Final stage of insect life" .)