Syndicate's caution about time taken by learner (6)
I believe the answer is:
cartel
'syndicate's' is the definition.
(cartel is a kind of syndicate)
'caution about time taken by learner' is the wordplay.
'caution' becomes 'care' ('care' can be a synonym of 'caution'**).
'about' means one lot of letters goes inside another.
'time' becomes 't'.
'taken by' is a charade indicator (letters next to each other).
'learner' becomes 'l'.
'care' enclosing 't' is 'carte'.
'carte'+'l'='CARTEL'
(Other definitions for cartel that I've seen before include "Market-fixing organisation" , "Firms operating together, illegally" , "controlling set of firms" , "Protective trade ring for claret" , "Manufacturer's association restricting competition" .)