Obstacles to getting horse in ship (5)
I believe the answer is:
snags
'obstacles' is the definition.
(snag is a kind of obstacle)
'getting horse in ship' is the wordplay.
'getting' is an insertion indicator.
'horse' becomes 'nag' (term for an old horse).
'in ship' becomes 'ss' (prefix in ship names eg SS Great Britain. I am not sure about the 'in' bit.).
'nag' going within 'ss' is 'SNAGS'.
'to' is the link.
Can you help me to learn more?
(Other definitions for snags that I've seen before include "Hitches" , "Unforeseen obstacles" , "Unexpected obstacles" , "Drawbacks" , "Problems" .)