Hold water (3,2)
'hold water' is the definition.
(I've seen this in another clue)
This is the entire clue.
(Other definitions for add up that I've seen before include "Total; make sense" , "Seem to be sensible" , "Seem consistent or reasonable - arithmetically?" , "Put together (numbers)" , "Do sums" .)
'hold water' is the definition.
(I've seen this in another clue)
This is all the clue.