Try to excuse old flame with blunter manner, so to speak (7,4)
I believe the answer is:
explain away
'try to excuse' is the definition.
I can't tell whether this defines the answer.
'old flame with blunter manner so to speak' is the wordplay.
'old flame' becomes 'ex' (an ex-lover).
'with' says to put letters next to each other.
'blunter manner' becomes 'pla' (I can't explain this - if you can you should give a lot more credence to this answer).
'so to speak' becomes 'in a way' (I've seen this in another clue).
'ex'+'pla'+'inaway'='EXPLAIN AWAY'
Can you help me to learn more?
(Other definitions for explain away that I've seen before include "Justify" , "Give justification for (something potentially embarrassing)" , "Offer excuses or reasons for mistakes" .)