theres an airbag behind there...dont wanna worry you but could be that....i think some air con gubbins is there as well....may be wrong but when i had mine off sure i seen something like air con pump thingys.
its only held on by 6 or so torks, u get at em by openin the door, like where the fuse pannel is on drivers side...think theres 3 more inside at the top. u might b able to track down the clicking.
HTH