Some lousy naps expected in gap between cells (7)
I believe the answer is:
synapse
'gap between cells' is the definition.
(a synapse is a gap between nerve cells)
'some lousy naps expected' is the wordplay.
'some' indicates a hidden word (some of the parts of the word are used).
'SYNAPSE' can be found hidden inside 'lousy naps expected'.
'in' is the link.
(Other definitions for synapse that I've seen before include "Where two nerve cells meet" , "Brain connection" , "It links cells" , "Nerve junction" , "Connection between nerve cells" .)