Go off after desk gets broken and run away (9)
I believe the answer is:
skedaddle
'run away' is the definition.
(skedaddling is a kind of running away)
'go off after desk gets broken' is the wordplay.
'go off' becomes 'addle' (eg an egg might addle).
'after' says to put letters next to each other.
'gets broken' indicates an anagram.
'desk' with letters rearranged gives 'sked'.
'addle' put after 'sked' is 'SKEDADDLE'.
'and' is the link.
(Other definitions for skedaddle that I've seen before include "Depart hurriedly" , "Scram" , "Depart quickly (colloq.)" , "In slang, go away quickly, scoot" , "take flight" .)