Expert putting head down and getting stuck into dealing with Neptune's orbit (5)
I believe the answer is:
ocean
'expert putting head down and' is the definition.
I can't tell whether this defines the answer.
'stuck into dealing with neptune's orbit' is the wordplay.
'stuck into' indicates putting letters inside.
'dealing with' becomes 'on'.
'neptune's orbit' becomes 'cea' (I am not sure about this - if you are sure you should believe this answer much more).
'on' going around 'cea' is 'OCEAN'.
'getting' acts as a link.
Can you help me to learn more?
(Other definitions for ocean that I've seen before include "Vast quantity of liquid" , "lot of liquid" , "eg Indian, Atlantic" , "Quantity of water" , "Large stretch of water" .)