Capricious sailor turning up in Morecambe, say (7)
I believe the answer is:
erratic
'capricious' is the definition.
(thesaurus)
'sailor turning up in morecambe say' is the wordplay.
'sailor' becomes 'tar' (tar is a kind of sailor).
'turning up' shows that the letters should be reversed in order.
'in' indicates putting letters inside.
'morecambe say' becomes 'eric' (Eric Morecambe is an example).
'tar' in reverse letter order is 'rat'.
'rat' put inside 'eric' is 'ERRATIC'.
(Other definitions for erratic that I've seen before include "Irregular, capricious" , "Variable" , "Inconsistent, shifting" , "Volatile" , "Unpredictable - car tire (anag)" .)