I suggest expert takes on problem (8)
I believe the answer is:
proposer
'i suggest' is the definition.
(I've seen this before)
'expert takes on problem' is the wordplay.
'expert' becomes 'pro' (short for professional).
'takes on' means one lot of letters go next to another.
'problem' becomes 'poser' (poser is a kind of problem).
'pro'+'poser'='PROPOSER'
(Other definitions for proposer that I've seen before include "Person putting motion forward" , "I'd suggest" , "Advocate" , "One putting forward motion" , "One making toast" .)