A little rhyme, an ingenious expression (7)
I believe the answer is:
meaning
'expression' is the definition.
(thesaurus)
'a little rhyme an ingenious' is the wordplay.
'a little' indicates the answer is hidden within the clue.
'MEANING' can be found hidden inside 'rhyme an ingenious'.
(Other definitions for meaning that I've seen before include "Definition (of 7 21?)" , "Sense intended" , "Purpose, intent" , "Import; purpose" , "Import; intending" .)