Go without food, finding a trace of mercury in salmon? (6)
I believe the answer is:
famish
'go without food' is the definition.
(to famish is to be extremely hungry)
'a trace of mercury in salmon?' is the wordplay.
'trace of' indicates taking the first letters.
'in' means one lot of letters goes inside another.
'salmon?' becomes 'fish' (salmon is a kind of fish).
The initial letter of 'mercury' is 'm'.
'a'+'m'='am'
'am' put within 'fish' is 'FAMISH'.
'finding' is the link.
(Other definitions for famish that I've seen before include "Suffer hunger" , "Make very hungry" , "Weaken (one) with hunger" , "Keep food from" , "Deprive of cheer" .)