Play half-back in hospital! (4)
I believe the answer is:
dock
'hospital' is the definition.
The definition and answer can be both man-made objects as well as being singular nouns.
Perhaps you can see a link between them that I don't see?
'play half-back' is the wordplay.
'play' becomes 'do' (both can mean to perform something).
'half' suggests halving the letters.
'back' halved is 'ck'.
'do'+'ck'='DOCK'
'in' is the link.
Can you help me to learn more?
(Other definitions for dock that I've seen before include "Where the accused is placed in court" , "Take pay from" , "In court, a prisoner stands in it" , "Cut off; plant" , "Platform on shore for access of ships and boats" .)