The very best computer, without hesitation, is sent back (5)
I believe the answer is:
cream
'the very best' is the definition.
(as in the cream of the crop)
'computer without hesitation is sent back' is the wordplay.
'computer' becomes 'mac' (as in an Apple Mac).
'without' indicates putting letters inside ('without' can be similar in meaning to 'outside').
'hesitation' becomes 'er' (sound used when hesitating).
'is sent back' is a reversal indicator.
'mac' enclosing 'er' is 'maerc'.
'maerc' written backwards gives 'CREAM'.
(Other definitions for cream that I've seen before include "An off-white shade" , "Very best; pale yellow" , "Top of milk or society" , "Dairy product" , "Best part of the milk" .)