Take over a thousand solid gold deer (7)
I believe the answer is:
roebuck
'deer' is the definition.
(roebuck is a kind of deer)
'take over a thousand solid gold' is the wordplay.
'take over' is a reversal indicator (I've seen 'taken over' mean this).
'a thousand' becomes 'K' (K can mean thousand, e.g. c0k).
'solid' becomes 'cube' (cube is a kind of solid).
'gold' becomes 'or' ('or' is the heraldic name for gold).
'k'+'cube'+'or'='kcubeor'
'kcubeor' backwards is 'ROEBUCK'.
(Other definitions for roebuck that I've seen before include "Stag" , "Providing venison" , "Being wild" , "Type of male deer" , "does partner" .)