Rush up to see the animals (4)
I believe the answer is:
deer
'the animals' is the definition.
(type of animals)
'rush up' is the wordplay.
'rush' becomes 'reed' (plants found by water).
'up' says the letters should be written backwards (in down clue: letters go upwards).
'reed' backwards is 'DEER'.
'to see' acts as a link.
(Other definitions for deer that I've seen before include "Hoofed grazing animal" , "Antlered animal" , "Red, roe or fallow" , "Wild animal" , "Perhaps fallow" .)