lovatts holiday crack the cryptic no.83

hi,am stuck on five clues and no matter how many times i come back to them i
just can't fathom the answer. 17d - Commanding Officer had midsummer on public land - C?R?O?
52d - Fish kept in inner layer - ??N?E? (i keep thinking TINNED)
49d - Specify military unit - ?N?A?L (is it ENTAIL)
55D - Defiantly flourish plate found under tumbledown barn - ?R???I?H
51a - French leader fell behind and became tired - ???G?N?
any help appreciated.thanks in advance