It may make basket cases of reclusive isolates, over from the east (5)
I believe the answer is:
osier
'it may make basket' is the definition.
(baskets can be made from osier wood)
'cases of reclusive isolates over from the east' is the wordplay.
'cases of' suggests removing the centre.
'isolates over' becomes 'iso' (I can't explain this - if you can you should give a lot more credence to this answer).
'from the east' is a reversal indicator (on a map from right to left).
'reclusive' with its middle taken out is 're'.
're'+'iso'='reiso'
'reiso' back-to-front is 'OSIER'.
Can you help me to learn more?
(Other definitions for osier that I've seen before include "Tree for basket making" , "... source of twigs to make baskets" , "Basket-maker" , "Bit of tree" , "Wetland willow" .)