Still in fear of returning, remains in American park (9,6)
I believe the answer is:
petrified forest
'american park' is the definition.
(US National Park)
'still in fear of returning remains' is the wordplay.
'still in fear' becomes 'petrified' (petrified literally means frozen or still in fear).
'returning' shows that the letters should be reversed in order.
'remains' becomes 'rest' (I can't explain this - if you can you should give a lot more credence to this answer).
'of' written backwards gives 'fo'.
'petrified'+'fo'+'rest'='PETRIFIED FOREST'
'in' acts as a link.
(Another definition for petrified forest that I've seen is " National park".)