Look up around ten former partners (4)
I believe the answer is:
exes
'former partners' is the definition.
(ex-lovers)
'look up around ten' is the wordplay.
'look' becomes 'see'.
'up' shows that the letters should be reversed in order (in down clue: letters go upwards).
'around' means one lot of letters goes inside another.
'ten' becomes 'X' (Roman numeral).
'see' back-to-front is 'ees'.
'ees' enclosing 'x' is 'EXES'.
(Other definitions for exes that I've seen before include "Former partners" , "former union members" , "Reduced claim from employer" , "Financial allowances" , "Expenses (abbrev.)" .)