Flat computer fit inside shirts (6)
I believe the answer is:
tablet
'flat computer' is the definition.
'tablet' can be an answer for 'computer'. I am not certain of the 'flat' bit.
'fit inside shirts' is the wordplay.
'fit' becomes 'able' (similar in meaning).
'inside' is an insertion indicator.
'shirts' becomes 'tt' (two T's - as in T-shirts).
'able' placed inside 'tt' is 'TABLET'.
Can you help me to learn more?
(Other definitions for tablet that I've seen before include "Prescription" , "Small bar of soap" , "Small pill or lozenge" , "PC" , "Pill - plaque" .)