The hare running wild on moorland, etc. (7)
I believe the answer is:
heather
'moorland etc' is the definition.
I can't tell whether this definition defines the answer.
'the hare running wild on' is the wordplay.
'running wild' is an anagram indicator.
'on' means one lot of letters goes inside another (as in clothing 'on' a person).
'hare' with letters rearranged gives 'hear'.
'the' put inside 'hear' is 'HEATHER'.
Can you help me to learn more?
(Other definitions for heather that I've seen before include "Moorland flora" , "Plant also called ling" , "Girl's name - ling" , "Moorland plant" , "Calluna vulgaris" .)