Clean back and front of tube that's burst (5)
I believe the answer is:
erupt
'that's burst' is the definition.
(synonyms)
'clean back and front of tube' is the wordplay.
'clean' becomes 'pure' (similar in meaning).
'back' says the letters should be written in reverse.
'and' means one lot of letters go next to another.
'front of' suggests taking the first letters (the letter at the front of the word).
The first letter of 'tube' is 't'.
'pure' written backwards gives 'erup'.
'erup'+'t'='ERUPT'
(Other definitions for erupt that I've seen before include "be active" , "Emit lava" , "Break out dramatically" , "Spurt lava" , "suddenly burst out" .)