Antelope pen erected, supplied with electric current (5)
I believe the answer is:
oribi
'antelope' is the definition.
(I've seen this before)
'pen erected supplied with electric current' is the wordplay.
'pen' becomes 'Biro' (Biro is a make of pen).
'erected' shows that the letters should be reversed in order (in a down clue, letters go up).
'supplied with' is a charade indicator (letters next to each other).
'electric current' becomes 'I' (physics symbol).
'biro' in reverse letter order is 'orib'.
'orib'+'i'='ORIBI'
(Other definitions for oribi that I've seen before include "Creature" , "small hoofed beast" , "Beastly sort" , "wild animal" , "type of antelope" .)