Dip in northwestern river curtailed after one minute (7)
I believe the answer is:
immerse
'dip in northwestern river' is the definition.
'immerse' can be an answer for 'dip' (I've seen this in another clue). I'm unsure of the 'in northwestern river' bit.
'curtailed after one minute' is the wordplay.
'curtailed' becomes 'merse' (I am not sure about this - if you are sure you should believe this answer much more).
'after' says to put letters next to each other.
'one' becomes 'i' (Roman numeral).
'minute' becomes 'm' (abbreviation).
'i'+'m'='im'
'merse' put after 'im' is 'IMMERSE'.
Can you help me to learn more?
(Other definitions for immerse that I've seen before include "Drown" , "Cover with water, dip into" , "Submerge in water as once for baptism" , "Engross" , "Plunge, dip, submerge" .)