Like user2357112's, but fixing the end element is simpler:

import collections
import itertools

def restricted_combinations(elements, sublist_length, combination_length):
    pool = collections.deque(maxlen=sublist_length-1)
    for elem in elements:
        for head in itertools.combinations(pool, combination_length - 1):
            yield (*head, elem)
        pool.append(elem)

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