Explosive sailor started at place of drudgery (4,4)
I believe the answer is:
salt mine
'place of drudgery' is the definition.
(I've seen this in another clue)
'explosive sailor started' is the wordplay.
I cannot really see how this works, but
'explosive' could be 'mine' (e.g. a landmine) and 'mine' is found in the answer.
'sailor' could be 'salt' (salt is a kind of sailor) and 'salt' is found within the answer.
No letters remain.
This explanation may well be incorrect...
'at' is the link.
Can you help me to learn more?
(Other definitions for salt mine that I've seen before include "Excavation" , "Ailments (anag)" , "Source of flavouring" , "Deep pit containing a white substance" .)