1.
Cold-blooded creature comes from Ecuador to join the soldiers on board, perhaps (9) - Ectotherm.
Ec(Ecuador), 'to', 'the', rm(Royal Marines - soldiers on board, perhaps).
2. Mark assuming I’m unable to return to a female
person’s sexual partner (11,5) - Significant Other.
Sign(Mark), if I Can't(assuming I’m unable to), ot(return to) and her(a female).
3. Net almost reached
online viewer (6) - Webcam.
Web(net), cam[e](almost reached).
4. Fleecing vipers, say, is uncommon without paying or
helping oneself (4-7) - Self-service
Anagram of(is uncommon) 'Fleecing vipers say' minus p.a.y.i.n.g.
5. Man, for example, just put down first
type of design (4,4) - Fair Isle
Isle(Man, for example) with fair(just) written before it(put down first).
Had quite a lot of time to spend today so was very happy to see your clues this week Jolan.
hope i'm correct with the rest of my post.