Resolute chap overwhelmed by dodgy data (7)
I believe the answer is:
adamant
'resolute' is the definition.
(both can mean determined)
'chap overwhelmed by dodgy data' is the wordplay.
'chap' becomes 'man' (chap can mean a man).
'overwhelmed by' is an insertion indicator (inserted letters get absorbed or overwhelmed).
'dodgy' is an anagram indicator (a dodgy or wrong order of the letters).
'data' is an anagram of 'adat'.
'man' placed within 'adat' is 'ADAMANT'.
(Other definitions for adamant that I've seen before include "Refusing to budge" , "Unyielding to requests, stubborn" , "unshakeable in purpose" , "Positive or intransigent" , "Refusing to change opinion" .)