4D - extra word 'Nick' both diminuitives of 'Nicholas'
4th thematic 3 letter Northern England word for meadow + abbrev for daughter inside common 4 letter word for ramble/roam - but it does not go with 1A - you are right on your answer (10 letters) which is the 5th thematic clue.
4th thematic goes with last across answer (5 letters)