Gold stolen by mischievous altar boy — might trial happen here? (10)
I believe the answer is:
Here is my best explanation:
'might trial happen here?' is the definition.
'gold stolen by mischievous altar boy' is the subsidiary indication.
'gold' becomes 'or'.
'stolen by' is an insertion indicator.
'mischievous' indicates an anagram.
'altarboy' anagrammed gives 'labatory'.
'or' put within 'labatory' is 'laboratory'.
(Other definitions for laboratory that I've seen before include "Where researchers work", "Where one investigates", "Language-learning facility", "Experimental facility", "Where litmus paper could be", "Place of scientific research", "In place of research", "workplace", "Experimental area" and "Place for experimentation".)