Charlie, downright eccentric! (5)
I believe the answer is:
crank
'eccentric' is the definition.
(crank is a kind of eccentric)
'charlie downright' is the wordplay.
'charlie' becomes 'c' (phonetic alphabet: alpha, bravo, charlie etc.).
'downright' becomes 'rank' (I've seen this before).
'c'+'rank'='CRANK'
(Other definitions for crank that I've seen before include "Turn a handle - weirdo" , "Turn (engine handle); eccentric" , "Person with strange and often aggressive ideas" , "Person with strange ideas, or machine part" , "Person of eccentric habits" .)