Massive test locking up first of offenders for racism? (7)
I believe the answer is:
bigotry
'racism?' is the definition.
(thesaurus)
'massive test locking up first of offenders' is the wordplay.
'massive' becomes 'big' (similar in meaning).
'test' becomes 'try' (synonyms).
'locking up' is an insertion indicator (I've seen this in other clues).
'first of offenders' becomes 'o' (1st letter of 'offenders').
'big'+'try'='bigtry'
'bigtry' going around 'o' is 'BIGOTRY'.
'for' acts as a link.
(Other definitions for bigotry that I've seen before include "Intolerant prejudice" , "Intolerance, prejudice on grounds of religion" , "Blind zeal" , "Stubborn prejudice" .)