The Guardian turning up after money? Must be nuts! (6)
I believe the answer is:
cashew
'nuts' is the definition.
'the guardian turning up after money?' is the wordplay.
'the guardian' becomes 'we' (the crossword setter and their Guardian colleagues).
'turning up' is a reversal indicator.
'after' is a charade indicator (letters next to each other).
'money?' becomes 'cash' (cash is a type of money).
'we' in reverse letter order is 'ew'.
'ew' after 'cash' is 'CASHEW'.
'must be' is the link.
(Other definitions for cashew that I've seen before include "snack perhaps" , "Kidney-shaped nut of tropical tree" , "Kind of nut" , "Kidney shaped nut" , "Edible nut" .)