Reportedly treasured, it's forced open (6)
I believe the answer is:
prised
This clue might be a double definition.
'reportedly treasured' is the first definition.
'prised' can be an answer for 'treasured' ('treasured'->'prized' is in my internal thesaurus and 'ize'->'ise'). I am unsure of the 'reportedly' bit.
'forced open' is the second definition.
(I've seen this before)
'it's' is the link.
Can you help me to learn more?
(Other definitions for prised that I've seen before include "Jemmied, levered" , "Levered open by spider" , "Levered (forcibly)" , "Forced open with leverage" , "Forced open with a lever" .)