Many, perhaps, seem relatively insensitive (6)
I believe the answer is:
number
'many' is the definition.
(thesaurus)
'seem relatively insensitive' is the wordplay.
I cannot really understand how this works, but
'insensitive' could be 'numb' (synonyms) and 'numb' is located in the answer.
The remaining letters 'er' is a valid word which might be clued in a way I don't understand.
This explanation may well be incorrect...
'perhaps' is the link.
Can you help me to learn more?
(Other definitions for number that I've seen before include "(Symbol for) quantity" , "Mathematical unit" , "Mathematical value" , "One possibly" , "For example, one" .)