Efficient computer with no frills (4)
I believe the answer is:
able
'efficient' is the definition.
(I've seen this in another clue)
'computer with no frills' is the wordplay.
'computer' becomes 'tablet'.
'with no frills' means to look at the middle letters (edge letters or 'frills' are removed).
The middle of 'tablet' is 'ABLE'.
(Other definitions for able that I've seen before include "Having the power, skill or means (to do something)" , "Having the skills and qualifications required" , "Qualified - expert" , "Competent, having ability" , "Fit as a seaman" .)