I now have quite a large collection of words in a text file (with definitions and so on). It would be very handy to be able to make this available in pleco on my iphone. Is this possible somehow?
if you save your text file onto your phone in the same format as the flashcards you can then go into the Pleco "Settings" screen -> Manage Dicts -> Add User -> Load Existing there you can select your file.
Almost, but if it's in a text file you'd actually use "Add New" instead of "Load Existing"; then, tap on the name of the new dictionary in Manage Dicts, and tap on the "Import" button to select and import the entries from your text file.