Having packed, finally decides to get married (6)
I believe the answer is:
stowed
'having packed' is the definition.
(packed or stowed away)
'finally decides to get married' is the wordplay.
'finally' suggests the final letters.
'get married' becomes 'wed' (synonyms).
The last letter of 'decides' is 's'.
's'+'to'+'wed'='STOWED'
(Other definitions for stowed that I've seen before include "Filled by packing tightly" , "Tidily stored away" , "Pack or store out of sight" , "loaded!" , "Put under the hatches" .)