Claim to have in one's possession (4)
I believe the answer is:
hold
This clue might be a double definition.
'claim' is the first definition.
(thesaurus)
'have in one's possession' is the second definition.
'hold' can be an answer for 'have' (synonyms). I'm not sure about the 'in one's possession' bit.
'to' acts as a link.
Can you help me to learn more?
(Other definitions for hold that I've seen before include "Grip" , "Keep in one's grasp" , "Maintain" , "Keep; cargo space" , "Have or possess" .)