Expensive drink dipped into by extremely large horse (13)
I believe the answer is:
steeplechaser
'horse' is the definition.
(I know that steeplechaser is a type of horse)
'expensive drink dipped into by extremely large' is the wordplay.
'expensive' becomes 'steep' (I've seen this before).
'drink' becomes 'chaser' (I've seen this before).
'dipped into by' is an insertion indicator.
'extremely' means to remove the middle letters (only the extremes of the word are used).
'large' with its centre removed is 'le'.
'steep'+'chaser'='steepchaser'
'steepchaser' enclosing 'le' is 'STEEPLECHASER'.
(Other definitions for steeplechaser that I've seen before include "Jumping racehorse" , "Competitive runner" , "Racehorse - athlete" , "Horse for jump races" , "Horse race participant" .)