Staggered online talks describing aquatic mammal (8)
I believe the answer is:
tottered
'staggered' is the definition.
'online talks describing aquatic mammal' is the wordplay.
'online talks' becomes 'ted' (TED Talks).
'describing' is an insertion indicator (describe can mean to form the outline of).
'aquatic mammal' becomes 'otter' (I've seen this before).
'ted' enclosing 'otter' is 'TOTTERED'.
(Other definitions for tottered that I've seen before include "Walked very unsteadily or shakily" , "Ruinous" , "Swayed and threatened to fall" .)