Flash application for computer device (5)
I believe the answer is:
mouse
'computer device' is the definition.
(a computer mouse)
'flash application' is the wordplay.
'flash' becomes 'mo' (both mean a very short period of time).
'application' becomes 'use' (I've seen this before).
'mo'+'use'='MOUSE'
'for' acts as a link.
(Other definitions for mouse that I've seen before include "shy and timid type" , "Rodent (for computing)" , "Small rodent and cursor controller" , "Quiet person" , "One sitting by computer" .)