Mixing up fruit refuse to pick up barrel held by strap (10)
I believe the answer is:
scrambling
'mixing up' is the definition.
'scrambling' can be an answer for 'mixing' (I've seen this before). I am not sure about the 'up' bit.
'fruit refuse to pick up barrel held by strap' is the wordplay.
'fruit refuse' becomes 'marc' (I've seen this before).
'to pick up' says the letters should be written backwards.
'barrel' becomes 'b' (industrial abbreviation).
'held by' means one lot of letters goes inside another.
'strap' becomes 'sling'.
'marc' backwards is 'cram'.
'cram'+'b'='cramb'
'cramb' put inside 'sling' is 'SCRAMBLING'.
Can you help me to learn more?
(Other definitions for scrambling that I've seen before include "Making speech unintelligible" , "Mixing" , "Motorcycle sport" , "irregular" , "getting flying forces going" .)