She's in the Wrens, presumably (5)
I believe the answer is:
jenny
'she's' is the definition.
I don't understand how the rest of the clue works.
Can you help me to learn more?
(Other definitions for jenny that I've seen before include "and 24 Down: Bird given female name" , "Female wren" , "Female donkey" , "Wren, Lind, or Seagrove" , "Female ass" .)