Such a dog will evidently take a drink! (3)
I believe the answer is:
lap
'drink' is the definition.
(to lap is to drink up)
'such a dog will evidently take a' is the wordplay.
'such a dog will evidently' becomes 'lp' (I am not sure about this - if you are sure you should give a lot more credence to this answer).
'take' is an insertion indicator.
'lp' enclosing 'a' is 'LAP'.
Can you help me to learn more?
(Other definitions for lap that I've seen before include "Stage - circuit" , "One round of the course" , "Single circuit of track" , "Circuit of racetrack" , "Knees" .)