25 A. Set off chasing German U-boat, losing ship (4) W?S?
27 A. Dodgy tabs found in stomach (4) ???M (possibly ??OM)
NB. This is a thematic puzzle. Six clues consist of wordplay only, with an associated word forming each entry. I don't know if these two clues are involved. (I have the 'relevant sentiment' running round the grid.)