Stand erect and extremely unbowed outside animal enclosure (5)
I believe the answer is:
upend
'stand erect' is the definition.
(I've seen this before)
'extremely unbowed outside animal enclosure' is the wordplay.
'extremely' suggests removing the centre (only the extremes of the word are used).
'outside' is an insertion indicator (some letters go outside others).
'animal enclosure' becomes 'pen' (I've seen this before).
'unbowed' with its centre removed is 'ud'.
'ud' enclosing 'pen' is 'UPEND'.
'and' is the link.
(Other definitions for upend that I've seen before include "Topple" , "Set upside down" , "Trip" , "change things drastically" , "Tip right over" .)