Indifferent to resident in attack (5)
I believe the answer is:
stoic
'indifferent' is the definition.
(thesaurus)
'to resident in attack' is the wordplay.
I cannot quite see how this works, but
'to' is found in the answer.
'attack' could be 'sic' (sicking is a kind of attacking) and 'sic' is located in the remaining letters.
This accounts for all the letters.
This explanation may well be incorrect...
Can you help me to learn more?
(Other definitions for stoic that I've seen before include "Greek in school" , "Someone seemingly indifferent to pleasure or pain" , "One showing endurance during adversity" , "not given to complaining" , "One who endures pain with equanimity" .)