Unsuspecting child initially rues loud eccentric (9)
I believe the answer is:
credulous
'unsuspecting' is the definition.
(thesaurus)
'child initially rues loud eccentric' is the wordplay.
'initially' suggests taking the first letters.
'eccentric' indicates an anagram.
The initial letter of 'child' is 'c'.
'rues'+'loud'='ruesloud'
'ruesloud' with letters rearranged gives 'redulous'.
'c'+'redulous'='CREDULOUS'
(Other definitions for credulous that I've seen before include "Likely to believe" , "Easily fooled" , "Gullible" , "Apt to believe without sufficient evidence" , "Too ready to believe things" .)