Animal used in many a laboratory (5)
I believe the answer is:
nyala
'animal' is the definition.
(I've seen this before)
'in many a laboratory' is the wordplay.
'in' indicates the answer is hidden within the clue.
'NYALA' can be found hidden inside 'many a laboratory'.
'used' acts as a link.
(Other definitions for nyala that I've seen before include "African animal" , "beast" , "Large African antelope" , "Ruminant" , "Antelope of southern Africa" .)