Girl's plants (5)
I believe the answer is:
flora
I believe this clue is a double definition.
'girl's' is the first definition.
'plants' is the second definition.
(I've seen this before)
(Other definitions for flora that I've seen before include "Lots of plants" , "Plants of a particular region" , "Form of life" , "For example, Miss Macdonald" , "__ MacDonald, heroine of the 1745 Jacobite rising" .)