Cloning seemed to have worked but left the rest of the 1.5TB unallocated, so was just like replacing a 500gb drive with another 500gb.
Inspecting the original drive in partition manager, it was split into many multiple partitions, so was not as simple as extending the other partitions and getting on with it. Had to reformat and do it the usual way 'as suggested.'
Further to this... the original drive was strangely unusable after the clone, with the PS4 giving an error, not allowing any safemode fix options either... did not think a cloning disk A onto disk B would at all affect drive A but somehow it did - data corrupted, not happened with the countless other drives i've cloned using this dock.
Though original disk was of use as normal in the PS4 after a reformat/reinstall. Stuck it in another pc for data storage just to make use of it.
The aim was to save time by not backing up all the installed games and media - Clone and resize partition.
End result, data on both drives were corrupted after cloning so had to reformat and reinstall firmware/all games and their updates anyway. And PS4 firmware install causes numerous partitions, so not simply resizeable to make use of new drive size either.
Tried cloning onto a different 1TB drive (from original 500GB drive) later to see if maybe the cloning process didn't go right but ended up with the same result of data on both drives becoming corrupted again, left it at that as had no patience to keep experimenting and wiped/fitted into a pc.