Hold up pen (5)
I believe the answer is:
stall
I believe this clue is a double definition.
'hold up' is the first definition.
(stalling is a kind of holding up)
'pen' is the second definition.
(thesaurus)
(Other definitions for stall that I've seen before include "Cowshed or stable" , "Booth; prevaricate" , "Equivocate" , "Block" , "Enclosure" .)