Irritability had to be self-controlled (9)
I believe the answer is:
temperate
'controlled' is the definition.
(I've seen this before)
'irritability had' is the wordplay.
'irritability' becomes 'temper' (synonyms).
'had' becomes 'ate' (e.g. I had an ice cream).
'temper'+'ate'='TEMPERATE'
'to be self' acts as a link.
This may not be correct. Some or all of it may belong to another bit of the clue.
Can you help me to learn more?
(Other definitions for temperate that I've seen before include "Abstemious" , "With mild climate" , "with balmy climate" , "sober" , "Moderate, mild" .)