Easily influenced (8)
'easily influenced' is the definition.
(I've seen this before)
This is all the clue.
(Other definitions for amenable that I've seen before include "Willing to comply" , "likely to cooperate - with 3a" , "Willing to be guided, being nameable" , "Flexible, agreeable" , "Ready to accept" .)
'easily influenced' is the definition.
(I've seen this before)
This is the entire clue.
(Other definitions for impressionable that I've seen before include "open to influence" , "Easily influenced" .)