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

'not initially getting more ill-tempered' is the definition.
I can't judge 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 give a lot more credence to this answer).
'rang' in reverse letter order is 'gnar'.
'gnar'+'lier'='GNARLIER'

'but' is the link.

Can you help me to learn more?