You have a VMDK on an NFS datastore, which expanded to hold files which have since been deleted. You are looking for a way to reclaim that space, correct?
VSC has a space reclamation utility for NFS datastores, but I think it requires an NTFS file system in the vmdk.
With 8.3 or later inline zero elimination should give the space back to the volume if you zero fill the whitespace on that disk, but the vmdk itself will still appear to be full size.
Otherwise zero fill the whitespace, then storage vmotion it to another datastore with "thin provisioned" selected as the disk format.