Fix me up with old men and a pen-name (3,2,5)
I believe the answer is:
nom de plume
'a pen-name' is the definition.
(I've seen this before)
'fix me up with old men' is the wordplay.
'fix' indicates anagramming the letters.
'with' means one lot of letters go next to another.
'me'+'up'+'old'+'men'='meupoldmen'
'meupoldmen' with letters rearranged gives 'NOM DE PLUME'.
'and' acts as a link.
(Other definitions for nom de plume that I've seen before include "Pen-name" , "False name" , "George Sand?" , "Author's pseudonym" , "Soubriquet" .)