Tall grass in which animals turned up (4)
I believe the answer is:
reed
'tall grass' is the definition.
(tall grass plant)
'animals turned up' is the wordplay.
'animals' becomes 'deer' (type of animals).
'turned up' is a reversal indicator.
'deer' back-to-front is 'REED'.
'in which' acts as a link.
(Other definitions for reed that I've seen before include "piece for organ" , "Type of grass" , "'It vibrates in a clarinet, say (4)'" , "It grows in water or marshy land" , "Tall woody grass" .)