Dictionary left with old idol (7)
I believe the answer is:
lexicon
'dictionary' is the definition.
(synonyms)
'left with old idol' is the wordplay.
'left' becomes 'l' (common abbreviation).
'with' means one lot of letters go next to another.
'old' becomes 'ex' (prefix meaning former or onetime).
'idol' becomes 'icon' (I've seen this before).
'l'+'ex'+'icon'='LEXICON'
(Other definitions for lexicon that I've seen before include "Dictionary of terms" , "(Classical) dictionary" , "Dictionary as of Greek or Hebrew" , "set of terms" , "Vocabulary - dictionary" .)