One taking inappropriate interest in single nurse we’re told (4,5)
I believe the answer is:
loan shark
'one taking inappropriate interest' is the definition.
(moneylender charging too much interest)
I don't understand how the rest of the clue works.
(Other definitions for loan shark that I've seen before include "Financial dealer" , "Money lender" , "Unscrupulous moneylender (colloq.)" , "One lends money at excessive rates of interest" , "Usurer" .)