Verbal, when rioting inmates caught (8)
I believe the answer is:
semantic
'verbal' is the definition.
(thesaurus)
'rioting inmates caught' is the wordplay.
'rioting' indicates an anagram (I've seen this in other clues).
'caught' becomes 'c' (cricket abbreviation).
'inmates' is an anagram of 'semanti'.
'semanti'+'c'='SEMANTIC'
'when' acts as a link.
(Other definitions for semantic that I've seen before include "Relating to meaning in language" , "Relating to the study of meaning" , "Of difference in meaning of words" , "Of meaning and connotation in language" , "Relating to the meaning of words" .)