pull the mains plug or isolate the power,
remove the condenser from the bottom of the appliance and carefully clean it,
if you can wash it using a garden hose pipe,even better,.
get your hand into the condenser housing (inside the dryer) and remove all,traces of lint/gunge etc.
dry the housing and the condenser as best you can then reassemble and see how it goes.
paul
March 2012