Job, perhaps one dividing half of sheep up (5)
I believe the answer is:
stoic
'job perhaps' is the definition.
(Job is a patient or stoic Biblical figure)
'one dividing half of sheep up' is the wordplay.
'one' becomes 'I' (Roman numeral).
'dividing' indicates putting letters inside.
'half of sheep' becomes 'cots' (I can't explain this - if you can you should give a lot more credence to this answer).
'up' says the letters should be written backwards (in down clue: letters go upwards).
'i' going inside 'cots' is 'ciots'.
'ciots' written backwards gives 'STOIC'.
(Other definitions for stoic that I've seen before include "Greek philosopher" , "Seeming unaffected by pleasure or pain" , "Resilient philosopher" , "One able to endure hardship; philosopher" , "One patient under misfortune" .)