Crew have to abandon second ship (5)
I believe the answer is:
posse
'crew' is the definition.
(I've seen this in another clue)
'to abandon second ship' is the wordplay.
I cannot quite understand how this works, but
'second' could be 's' (common abbreviation) and 's' is located in the answer.
The remaining letters 'pose' is a valid word which might be clued in a way I don't understand.
This explanation may well be incorrect...
'have' acts as a link.
Can you help me to learn more?
(Other definitions for posse that I've seen before include "Group temporarily established for some purpose" , "Band of lawmen" , "power" , "Sheriff's team" , "Group of sheriff's men" .)