Practical program deliberately gave wrong answer (7)
I believe the answer is:
applied
'practical' is the definition.
(similar in meaning)
'program deliberately gave wrong answer' is the wordplay.
'program' becomes 'app' (type of computer program).
'deliberately gave wrong answer' becomes 'lied' (lie can mean to knowingly give a wrong answer).
'app'+'lied'='APPLIED'
(Other definitions for applied that I've seen before include "Assigned < practical" , "Went for university place" , "Useful" , "Put into service, made work" , "Administered" .)