Their duty may not be at the coast? (13)
I believe the answer is:
inlandrevenue
'their duty may not' is the definition.
I don't know anything about this answer so I cannot tell whether it can be defined by this definition.
'at the coast?' is the wordplay.
I cannot quite understand how this works, but
'at' could be 'in' (synonymous in some cases - eg at school, in school) and 'in' is found within the answer.
This explanation may well be incorrect...
'be' is the link.
Can you help me to learn more?
(Other definitions for inlandrevenue that I've seen before include "Government tax department" , "Government department collecting direct taxes" .)