One steering boat in trouble, overwhelmed by a leaking hole (6)
I believe the answer is:
tiller
'one steering boat' is the definition.
The definition and answer can be both man-made objects as well as being singular nouns.
Perhaps there's an association between them I don't understand?
'trouble overwhelmed by a leaking hole' is the wordplay.
'trouble' becomes 'i'll' (synonyms).
'overwhelmed by' means one lot of letters goes inside another (inserted letters get absorbed or overwhelmed).
'a leaking hole' becomes 'ter' (I am not sure about this - if you are sure you should give a lot more credence to this answer).
'ill' inserted within 'ter' is 'TILLER'.
'in' is the link.
Can you help me to learn more?
(Other definitions for tiller that I've seen before include "Farmer" , "Boat's steering bar" , "Handle for turning rudder" , "Bar used to turn rudder in small boat" , "Lever to move a boat's rudder" .)