Lie acted in a way that was subtle (8)
I believe the answer is:
delicate
'subtle' is the definition.
(similar in meaning)
'lie acted in a way' is the wordplay.
'in a way' indicates an anagram.
'lie'+'acted'='lieacted'
'lieacted' with letters rearranged gives 'DELICATE'.
'that was' is the link.
(Other definitions for delicate that I've seen before include "Not strong or healthy" , "Fine and dainty" , "Fragile - tactful" , "ticklish!" , "Weak" .)