Setter for example sent up Caesar's language (7)
I believe the answer is:
gelatin
'setter' is the definition.
(substance which sets or hardens)
'example sent up caesar's language' is the wordplay.
'example' becomes 'eg' (short for 'exempli gratia', 'for example' in Latin).
'sent up' shows that the letters should be reversed in order.
'caesar's language' becomes 'latin' (I've seen this before).
'eg' written backwards gives 'ge'.
'ge'+'latin'='GELATIN'
'for' is the link.
(Other definitions for gelatin that I've seen before include "something gluey" , "Jelling agent" , "Setter" , "Animal protein used in foods, glues, emulsions, etc" , "Organic glue used in foodstuffs" .)