Captain may need this gun with plan to purchase one (9,5)
I believe the answer is:
automatic pilot
'captain may need this gun with plan to purchase one' is the definition.
The answer and definition can be both man-made objects as well as being singular nouns.
Perhaps you can see an association between them that I can't see?
'gun with plan to purchase one' is the wordplay.
I cannot quite understand how this works, but
'gun' could be 'automatic' (automatic is a kind of gun) and 'automatic' is found in the answer.
'one' could be 'i' (Roman numeral) and 'i' is present in the answer.
'plan' could be 'plot' (plot is a kind of plan) and 'plot' is present in the remaining letters.
No letters remain.
This may be the basis of clue (or it may be nonsense).
Can you help me to learn more?
(Other definitions for automatic pilot that I've seen before include "George" , "Device keeping aircraft on course" .)