Irascible recreating Saturn on cake (12)
I believe the answer is:
cantankerous
'irascible' is the definition.
(I've seen this before)
'recreating saturn on cake' is the wordplay.
'recreating' is an anagram indicator (I've seen 'recreated' mean this).
'saturn'+'on'+'cake'='saturnoncake'
'saturnoncake' is an anagram of 'CANTANKEROUS'.
(Other definitions for cantankerous that I've seen before include "Cross" , "Irritable" , "Stubbornly obstructive" , "Crabby" , "Grumpy" .)