Boat departs, given access to fuel? It's undecided (3,6)
I believe the answer is:
sub judice
'undecided' is the definition.
(legal term)
'boat departs given access to fuel?' is the wordplay.
'boat' becomes 'sub' (I've seen this before).
'departs' becomes 'd' (common abbreviation e.g. train timetables).
'given access to' is an insertion indicator.
'fuel?' becomes 'juice' (I've seen this before).
'd' put within 'juice' is 'judice'.
'sub'+'judice'='SUB JUDICE'
'it's' acts as a link.
(Other definitions for sub judice that I've seen before include "Under consideration by the courts - don't comment on it" , "Still before court" , "Under consideration by court - don't comment" .)