Secluded trees held nuts (9)
I believe the answer is:
sheltered
'secluded' is the definition.
(I've seen this before)
'trees held nuts' is the wordplay.
'nuts' indicates an anagram (nuts can mean crazy).
'trees'+'held'='treesheld'
'treesheld' is an anagram of 'SHELTERED'.
(Other definitions for sheltered that I've seen before include "safe from the elements" , "Covered" , "in such accommodation?" , "Protected or shielded" , "Protected from danger or bad weather" .)