Make allowances, keeping it up with increasing rancour (7)
I believe the answer is:
cattier
'make allowances keeping it up with increasing rancour' is the definition.
I can't judge whether this defines the answer.
'keeping it up with increasing rancour' is the wordplay.
'keeping' means one lot of letters goes inside another (some letters kept inside).
'up' is an anagram indicator (letters get chucked up).
'with increasing rancour' becomes 'cater' (I am not sure about this - if you are sure you should give a lot more credence to this answer).
'it' anagrammed gives 'ti'.
'ti' placed within 'cater' is 'CATTIER'.
Can you help me to learn more?
(Another definition for cattier that I've seen is " more spiteful".)