Shag explorer lying back, commander (7)
I believe the answer is:
tobacco
'shag' is the definition.
(I've seen this before)
'explorer lying back commander' is the wordplay.
'explorer' becomes 'cabot' (I've seen this before).
'lying back' says the letters should be written in reverse.
'commander' becomes 'co'.
'cabot' backwards is 'tobac'.
'tobac'+'co'='TOBACCO'
(Other definitions for tobacco that I've seen before include "Nicotine-rich plant" , "Pipe leaves" , "Leaves prepared for smoking" , "often considered a weed" , "Cob coat to smoke" .)