Plan sure to capture very loud bear (6)
I believe the answer is:
suffer
'bear' is the definition.
('suffer' can be a synonym of 'bear')
'plan sure to capture very loud' is the wordplay.
'plan' indicates anagramming the letters (I've seen this in other clues).
'to capture' means one lot of letters goes inside another.
'very loud' becomes 'ff' (musical abbreviation).
'sure' anagrammed gives 'suer'.
'suer' enclosing 'ff' is 'SUFFER'.
(Other definitions for suffer that I've seen before include "Undergo, endure" , "Be affected by (illness)" , "experience sore head?" , "Endure; hurt" , "Bear" .)