Vixen maybe in grass, rolling over, under control (8)
I believe the answer is:
reindeer
'vixen maybe' is the definition.
I can't tell whether this definition defines the answer.
'grass rolling over under control' is the wordplay.
'grass' becomes 'reed' (type of grass plant).
'rolling over' says the letters should be written backwards.
'under' means one lot of letters go next to another (in a down clue, some letters go below others).
'control' becomes 'rein' (rein is a kind of control).
'reed' in reverse letter order is 'deer'.
'deer' after 'rein' is 'REINDEER'.
'in' is the link.
Can you help me to learn more?
(Other definitions for reindeer that I've seen before include "Domesticated animals" , "Rudolph, for instance" , "Dancer, for one" , "Santa's Prancer, say" , "wild animal" .)