Throw party, performing Blue Moon on dropping tab (14)
I believe the answer is:
discombobulate
'throw' is the definition.
(synonyms)
'party performing blue moon on dropping tab' is the wordplay.
'party' becomes 'disco' (I've seen this before).
'performing' indicates an anagram.
'dropping' is a deletion indicator (some letters drop out).
'blue'+'moon'='bluemoon'
'bluemoon' with 'on' removed is 'bluemo'.
'bluemo'+'tab'='bluemotab'
'bluemotab' anagrammed gives 'mbobulate'.
'disco'+'mbobulate'='DISCOMBOBULATE'
(Other definitions for discombobulate that I've seen before include "Upset" , "Throw" , "Confuse" , "cause confusion" , "rattle?" .)