Expensive, removing the first trickle (4)
I believe the answer is:
seep
'first trickle' is the definition.
'seep' can be an answer for 'trickle' (I've seen this in another clue). I am not sure about the 'first' bit.
'expensive removing the' is the wordplay.
'expensive' becomes 'steep' (I've seen this before).
'removing' is a deletion indicator.
'the' becomes 't' (the is pronounced as a 't' sound in some dialects).
'steep' with 't' taken out is 'SEEP'.
Can you help me to learn more?
(Other definitions for seep that I've seen before include "Come out slowly" , "Trickle through slowly" , "Leak gradually" , "Of liquid, ooze slowly out" , "dribble away" .)