Simple tea set replaced (6)
I believe the answer is:
chaste
'simple' is the definition.
(I've seen this before)
'tea set replaced' is the wordplay.
'tea' becomes 'cha' (cha is a type of tea).
'replaced' indicates an anagram.
'set' is an anagram of 'ste'.
'cha'+'ste'='CHASTE'
(Other definitions for chaste that I've seen before include "She-cat could be virtuous" , "Pure - virtuous" , "Everlasting" , "Like Diana" , "Refraining from sex" .)