Passable actor going round a one-time king’s hiding-place (3,4)
I believe the answer is:
oak tree
'one-time king's hiding-place' is the definition.
(Charles II famously hid in an oak tree)
'passable actor going round a' is the wordplay.
'passable' becomes 'ok'.
'actor' becomes 'tree' (Herbert Beerbohm Tree, 19th-century actor).
'going round' is an insertion indicator (some letters go around others).
'ok'+'tree'='oktree'
'oktree' enclosing 'a' is 'OAK-TREE'.
(Other definitions for oak tree that I've seen before include "wood source?" , "Old plant (round which to tie a yellow ribbon?)" , "royal hiding place evidently" , "Source of acorns" , "famous royal hideout" .)