Catch, we’re told, glimpses (4)
I believe the answer is:
sees
'glimpses' is the definition.
(I've seen this in another clue)
'catch we're told' is the wordplay.
'catch' becomes 'seize' (I've seen this before).
'we're told' shows a homophone (sound like).
'seize' sounds like 'SEES'.
(Other definitions for sees that I've seen before include "Notices" , "Understands" , "Spots" , "Observes or perceives" , "Observes the bishops' domains" .)