A long time to get silver bearings (4)
I believe the answer is:
ages
'a long time' is the definition.
(ages can mean a very long time)
'get silver bearings' is the wordplay.
'get' says to put letters next to each other.
'silver' becomes 'Ag' (Ag is the chemical symbol for silver).
'bearings' becomes 'es' (I can't explain this - if you can you should give a lot more credence to this answer).
'ag' next to 'es' is 'AGES'.
'to' is the link.
Can you help me to learn more?
(Other definitions for ages that I've seen before include "... of Man, according to WB Yeats" , "Yonks" , "Aeons" , "Epochs" , "A long time (colloq.)" .)