Spry outsiders cover the distance, looking cheerful all the while (6)
I believe the answer is:
smiley
'looking cheerful all the while' is the definition.
I can't tell whether this defines the answer.
'spry outsiders cover the distance' is the wordplay.
'outsiders' suggests removing the centre (only the letters on the outside of the word remain).
'cover' indicates putting letters inside.
'the distance' becomes 'mile' (mile is a unit of distance).
'spry' with its middle taken out is 'sy'.
'sy' enclosing 'mile' is 'SMILEY'.
Can you help me to learn more?
(Other definitions for smiley that I've seen before include "Cheerful emoticon" , "sounds cheerful" , "Spymaster" , "Grinning face symbol" .)