Long to join Conservative party (5)
I believe the answer is:
crave
'long' is the definition.
(thesaurus)
'join conservative party' is the wordplay.
'join' means one lot of letters go next to another.
'conservative' becomes 'c' (abbreviation commonly used in UK politics).
'party' becomes 'rave' (I've seen this before**).
'c' put next to 'rave' is 'CRAVE'.
'to' acts as a link.
(Other definitions for crave that I've seen before include "Have strong desire for, or beg as for mercy" , "Powerfully desire" , "need, desperately" , "Have strong urge" , "Really want" .)