Impressionable one in factory (6)
I believe the answer is:
pliant
'impressionable' is the definition.
('pliant' can be similar in meaning to 'impressionable')
'one in factory' is the wordplay.
'one' becomes 'i' (Roman numeral).
'in' indicates putting letters inside.
'factory' becomes 'plant' (I've seen this before).
'i' placed within 'plant' is 'PLIANT'.
(Other definitions for pliant that I've seen before include "Adaptable" , "easily controlled" , "Plastic" , "Tractable" , "easily modified" .)