Tending to shake, a bit like a flight case? (9)

'tending to shake a bit' is the definition.
(likely to shake or quiver)

'like a flight case?' is the wordplay.
I cannot quite understand how this works, but
'like' could be 'ish' (similar in meaning) and 'ish' is found within the answer.
'case?' could be 'quiver' (quiver is a kind of case) and 'quiver' is found in the answer.
This accounts for all the letters.
This explanation may well be incorrect...