Called back, cross, but not initially getting more ill-tempered (8)

'not initially getting more ill-tempered' is the definition.
I can't tell whether this definition defines the answer.

'called back cross' is the wordplay.
'called' becomes 'rang' (called on the phone).
'back' shows that the letters should be reversed in order.
'cross' becomes 'lier' (I can't explain this - if you can you should believe this answer much more).
'rang' back-to-front is 'gnar'.
'gnar'+'lier'='GNARLIER'

'but' acts as a link.

Can you help me to learn more?