Practical software was deceptive (7)
I believe the answer is:
applied
'practical' is the definition.
(similar in meaning)
'software was deceptive' is the wordplay.
I cannot really see how this works, but
'software' could be 'app' (I've seen this before) and 'app' is found in the answer.
The remaining letters 'lied' is a valid word which might be clued in a way I don't understand.
This explanation may well be incorrect...
Can you help me to learn more?
(Other definitions for applied that I've seen before include "put to practical use" , "implemented" , "Was relevant" , "Type of science" , "sort of maths" .)