Most insensitive to make contact with us about first oversight (7)
I believe the answer is:
callous
'most insensitive' is the definition.
'callous' can be an answer for 'insensitive' (similar in meaning). I am not certain of the 'most' bit.
'contact with us about first oversight' is the wordplay.
'contact' becomes 'call'.
'with' means one lot of letters go next to another.
'about' is a charade indicator (letters next to each other).
'first oversight' becomes 'o' (1st letter of 'oversight').
'us' put after 'o' is 'ous'.
'call' next to 'ous' is 'CALLOUS'.
'to make' is the link.
Can you help me to learn more?
(Other definitions for callous that I've seen before include "Hard-hearted" , "Cruelly unfeeling" , "Cruel or unsympathetic" , "Insensitive, cruel" , "Cruel and unfeeling" .)