Cells transformed into a show of appreciation (7)
I believe the answer is:
ovation
'a show of appreciation' is the definition.
(I've seen this before)
'cells transformed into' is the wordplay.
'cells' becomes 'ova' (ovum is a kind of cell).
'transformed' indicates anagramming the letters.
'into' is an anagram of 'tion'.
'ova'+'tion'='OVATION'
(Other definitions for ovation that I've seen before include "Show of appreciation" , "enthusiastic response" , "Long period of applause" , "Long bout of applause" , "Enthusiastic reception" .)