Happen to swallow pastry holder (8)
I believe the answer is:
occupier
'holder' is the definition.
The definition and answer can be both people as well as being singular nouns.
Maybe you can see a link between them that I can't see?
'happen to swallow pastry' is the wordplay.
'happen' becomes 'occur' (synonyms).
'to swallow' means one lot of letters goes inside another.
'pastry' becomes 'pie' (pie is a kind of pastry).
'occur' enclosing 'pie' is 'OCCUPIER'.
Can you help me to learn more?
(Other definitions for occupier that I've seen before include "One in residence" , "Squatter" , "One inhabiting a place" , "Resident" , "Person in position" .)