Jenny’s an architect (4)
I believe the answer is:
wren
I believe this is a double definition.
'jenny's' is the first definition.
(jenny wren is another name for a wren)
'an architect' is the second definition.
(Sir Christopher Wren)
(Other definitions for wren that I've seen before include "Small brown bird 'hunted' on St Stephen's Day" , "Troglodytes troglodytes" , "serving girl" , "Sir Christopher -, architect of St Paul's" , "Small active brown northern hemisphere bird" .)